RV Door Lock Fitment: Three Measurements Before You Buy

RV Door Lock Fitment: Three Measurements Before You Buy

RV Door Lock Fitment: Three Measurements Before You Buy

RV door locks almost never fail on features. They fail on fitment. People buy the one with the fingerprint reader, the one with the app, the one with the longer remote range — and then find out the opening in their door is two millimeters off, or that the handle points the wrong way, or that the lock body hits the window.

There are three measurements that decide whether a lock fits, plus a fourth that nobody thinks to take. All four take about five minutes with a tape measure. This guide covers what to measure, how to read the numbers the product pages actually give you, and which of three locks suits which result — because the three do not fit the same doors.

1. Why Fitment Is the Whole Decision
2. Measurement 1: The Cutout
3. Measurement 2: Door Thickness
4. Measurement 3: Which Way the Hinges Are
5. Measurement 4: The Clearance Nobody Takes
6. The Three Locks, Side by Side
7. Choosing From Your Measurements
8. Install Day: Batteries and Backups
9. Frequently Asked Questions
10. The Bottom Line

1. Why Fitment Is the Whole Decision

A door lock is one of the few RV purchases where the feature list matters less than the geometry. Every lock in this category does the same core job — it opens, it locks, it keeps the door shut while you drive. The features are differences of convenience. The fitment is a difference of possible or impossible.

That asymmetry should shape how you shop. Read the measurements first and the features second, because a lock with five unlock methods that does not seat in your door has zero unlock methods.

If you are still deciding whether a keyless lock is worth doing at all, that is a different question and we have already made that argument in our guide to smart RV upgrades. The short version: the factory lock is the cheapest component on the coach, it is keyed alike with every other coach at the campground, and replacing it takes about twenty minutes. This article assumes you are past that and now need the right one.

2. Measurement 1: The Cutout

The cutout is the rectangular hole in the door that the lock passes through. Measure the opening itself — height and width — with the lock removed, or measure the existing lock's face plate if you cannot get it out yet. Write the numbers down in millimeters.

Here is where it gets interesting, and where this article earns its place. The RV industry calls this opening 3.75 by 2.75 inches. That is the name you will see on listings, and it is the name people repeat to each other.

But 3.75 inches is 95.25 mm, and the actual measured openings on these product pages are 92 mm high by 68 to 70 mm wide. Convert 92 mm back and you get 3.62 inches, not 3.75. The two figures disagree by roughly three millimeters — and on a lock with a stated tolerance of plus or minus one to two millimeters, three millimeters is the difference between seating and not seating.

The practical rule: measure the hole, compare in millimeters, and treat any inch figure as a nickname rather than a specification. If your measurement is within a millimeter or two of 92 mm high and 68 to 70 mm wide, you are in the standard fitment family and all three locks below are candidates on this dimension alone.

3. Measurement 2: Door Thickness

The second measurement is the thickness of the door itself, taken at the lock opening. This one is less prone to confusion because all three products state it in both units, but the ranges are not identical:

A door at 36 mm fits all three. A door at 33 mm fits KD01 and JD but is outside the D1-B range. That three-millimeter band at the thin end is the only place this measurement eliminates anything, and it is worth checking precisely because most people assume all RV doors are the same thickness. They are not — a door with an inner panel or insulation differs from a bare one.

4. Measurement 3: Which Way the Hinges Are

This is the measurement people skip, and it is the one that produces the most useless purchase: a lock that fits the hole perfectly but points the handle the wrong way. It cannot be fixed by installation. The part is handed.

The method is simple and the product pages state it identically: stand outside your RV, facing the door. Look at the hinges.

• Hinges on the left — you need a left-hand lock.
• Hinges on the right — you need a right-hand lock.

Standing on the outside facing the door is the detail that matters, because the answer flips if you do it from inside. Two people measuring the same door from opposite sides get opposite answers, which is exactly how a return happens.

So if your hinges are on the left, your shortlist is effectively one product: the D1-B in its left-hand version. That is not a limitation of the range so much as a fact worth knowing before you fall in love with a fingerprint reader.

5. Measurement 4: The Clearance Nobody Takes

The cutout is the hole. The clearance is the space around it, and lock bodies are wider than their cutouts — they have to be, because the electronics and the bolt mechanism live outside the hole. On a door with a window close to the lock, this is the measurement that decides everything.

The three products are not the same here, and one of them does not state the figure at all:

The JD page turns this into an explicit test it calls Critical Clearance A: measure from the cutout's right edge to the window's left edge. Above 8 cm, it fits. At 8 cm or less, the lock body will hit the window and the page says plainly not to order. KD01 asks for at least 6 cm of clear space on the right for the same reason.

That is why the JD body being 200 mm long matters. It is the largest of the three, and the clearance requirement scales with it. If your door is compact — a camper van door, a small trailer with a window set close to the handle — this measurement eliminates the widest lock before any feature comparison begins.

6. The Three Locks, Side by Side

With fitment settled, the remaining differences are real and worth comparing on their own terms. These are the figures exactly as the product pages state them.

Read that table with the "not stated" entries in mind. D1-B does not publish a clearance or an operating temperature; KD01 does not publish an IP number. Those are not omissions on my part, and I have not filled the gaps with the other products' figures — a lock's weather rating is its own, not its neighbour's.

Three differences are worth calling out because they affect daily use rather than spec-sheet bragging. The D1-B runs 3 to 4 months on a set of batteries, which is short enough that its own page recommends replacing them every three months. The KD01 and JD take longer, with JD claiming 6 to 12. And only the JD ships with batteries included — D1-B and KD01 both require 4 × AA before first use, which is the kind of detail that turns an install evening into a second trip to the store.

GRUNDIG KD01 4-in-1 Keyless RV Door Lock

• Fingerprint, PIN, remote fob and backup key — four ways in
• Unlimited fingerprints and codes, no preset limit
• Remote range up to 20 m (65 ft) with line of sight
• 4–8 digit passcode, factory default 1234
• Zinc-alloy cylinder in an all-metal powder-coated housing
• Fits 32–38 mm doors, right-hand opening

7. Choosing From Your Measurements

Once you have four numbers, the decision usually makes itself. Here is how the cases fall out.

Hinges on the left

The D1-B in its left-hand version is your option in this range. It gives you remote, keypad and mechanical key — no fingerprint, no app — and it is the lightest of the three at 750 g. Budget for batteries, since the page states they are not included.

Hinges on the right, window close to the lock

Measure the Critical Clearance A distance before anything else. If it is 8 cm or less, the JD body will hit the window and you should not order it. The KD01 asks for 6 cm rather than 8, so on a tight door it may fit where the wider lock does not — but note that the D1-B does not publish a clearance figure at all, so on a tight door that one needs a conversation with the seller rather than an assumption.

Hinges on the right, plenty of room, want the most ways in

The JD series is the flexible one here because it is three products in one listing: JD01 gives you keypad, key and fob; JD02 adds a BYD semiconductor fingerprint sensor that reads in under a second; JD03 adds Bluetooth app control through Tuya Smart, so the door opens as you walk up. All three share the same body, the same IP65 rating and the same 4 × AA power.

Hinges on the right, want the longest remote range

The KD01's 20 m (65 ft) is the longest of the three, against 15 m for the D1-B and 5–10 m for the JD. If you want to unlock from inside the tow vehicle or from across a campsite, that figure is the one to compare — all three are quoted as requiring a clear line of sight, so metal in the way shortens every one of them.

8. Install Day: Batteries and Backups

All three are direct replacements with no wiring, and the stated install time is in the twenty to thirty minute range. The details that decide whether the evening goes smoothly are smaller than that.

• Bring 4 × AA batteries. D1-B and KD01 both state they are not included. Only the JD ships with them.
• Keep a backup key outside the coach. All three include two mechanical keys, and all three pages say the same thing: store them outside the RV, never locked inside. A backup key in the glovebox of a locked motorhome is not a backup.
• Change the default code. D1-B and KD01 both ship with 1234. Changing it takes four steps on the D1-B and is a menu setting on the KD01.
• Know the emergency power method. The JD has 9V battery contact points on the outside of the keypad for a dead-battery entry. The D1-B and KD01 rely on the mechanical key as their stated fallback.
• Check the strike plate alignment. The KD01 ships with a strike plate; the others ship with a mounting plate. If your frame's strike is worn, the new lock may latch loosely — worth a look before you tighten everything down.

If your coach also needs the other wear items — the water heater parts, the toilet seals, the blowout adapter — our guide to the RV parts that fail on a schedule covers what wears out predictably and how to match part numbers on those. Door locks are not on that list, incidentally, because a lock does not wear out on a schedule — it either fits or it does not.

9. Frequently Asked Questions

No — you have the standard door, and the inch label is approximate. 3.75 inches converts to 95.25 mm, but the actual measured openings stated on these product pages are 92 mm high by 68 to 70 mm wide. The two figures disagree by about three millimeters. Measure in millimeters and compare in millimeters; treat the inch name as a nickname rather than a specification.

Stand outside your RV, facing the door, and look at the hinges. Hinges on the left means you need a left-hand lock; hinges on the right means right-hand. Doing this from inside the coach gives you the opposite answer, which is the usual reason people order the wrong one. Of the three locks here, only the D1-B is sold in both versions.

Measure from the cutout's right edge to the window's left edge. The JD page calls this Critical Clearance A and states that above 8 cm it fits, while at 8 cm or less the lock body will hit the window. The KD01 asks for at least 6 cm of clear space on the right. The D1-B does not publish a clearance figure, so on a tight door that one needs confirming with the seller.

The JD does. The D1-B and KD01 both state that 4 × AA batteries are not included, so have them ready before you start. The JD states 6 to 12 months of battery life, the KD01 about 4 to 6 months, and the D1-B about 3 to 4 months with a recommendation to replace every three months.

All three include two mechanical backup keys, and all three pages say the key works even with dead batteries. The JD additionally has 9V battery contact points on the outside of the keypad so you can temporarily power it. Keep a backup key stored outside the coach rather than inside it.

It depends which lock. KD01 and the JD series are both stated for 32–38 mm doors. The D1-B is stated for 35–38 mm, so a door at 33 mm is outside its range. Measure the door at the lock opening rather than assuming all RV doors match.

10. The Bottom Line

Measure four things in this order: the cutout in millimeters, the door thickness, which side the hinges are on from outside, and the clear space to the right of the opening. Each one eliminates products, and the order matters because it stops you comparing features on a lock that was never going to fit.

If your hinges are on the left, the decision is made for you — the D1-B is the only left-hand option here. If they are on the right, the choice comes down to clearance and how many ways you want to get in: the KD01 if you want a fingerprint and the longest remote range, the JD series if you want app control or the longest battery life, and the D1-B if you want the lightest and simplest of the three.

And whatever you choose, measure the hole with a tape before you order. The single most common way this purchase goes wrong is not a defective lock — it is a lock that was correct in every way except the shape of the hole it had to go into.

Measure First, Then Choose

Cutout, thickness, handing and clearance — four numbers decide which of these three fits your door.

Disclaimer: Cutout dimensions, door thickness ranges, handing and clearance requirements vary by lock model and by door. Measure your own door before ordering and confirm the manufacturer's stated figures on the product page. If your door has a window, an unusual frame or a non-standard opening, confirm fitment with the seller before purchase.

Facts Index