You picked a smart lock. It looked great, the price was fair, and the reviews were solid. Then the installer arrived and said one line that ruined the day. "This won't fit your door." Now you are stuck with a box you cannot return easily. This happens more than people admit, and the reason is almost always the door, not the lock.

Short answer: Door material, door thickness, and existing cutout decide which smart lock fits. Wooden doors suit most smart locks. Steel doors need a mortise model and careful drilling. Glass doors usually cannot take a standard smart lock at all and need a rim lock or a frame mounted option. Measure thickness and cutout before you buy.

Last updated: September 2026. Smart lock prices and model compatibility can change. Check the product page for exact door requirements before ordering.

What's in this post

• The three things that decide fit
• Wood, steel and glass doors explained
• Quick fit table
• The measurement mistake most people make
• Who should not buy a standard smart lock
• Common questions

The Three Things That Decide Fit

Forget brand for a minute. Only three things decide whether a smart lock will fit your door.

One: the material. Wood, steel and glass behave differently. Wood can be drilled and chiselled easily. Steel resists drilling and usually needs a mortise lock that drops into a pocket. Glass cannot be drilled at all without risking cracks, so the lock has to mount on the frame or use an existing hole.

Two: the thickness. Smart locks are built for a specific door thickness range, commonly 35 to 55 mm [VERIFY by model]. A thin door makes the lock wobble. A thick door means the bolts will not reach through. Neither is fixable with force.

Three: the existing cutout. If your door already has a lock hole or a mortise pocket, the new lock must match that size. A mortise is a rectangular slot cut into the door edge where the lock body sits. If the new lock's mortise is bigger than the old one, you can enlarge the pocket. If it is smaller, you have a gap and the door will not sit right.

Get these three right and almost any smart lock fits. Get one wrong and nothing works

Wood, Steel and Glass Doors Explained

Wooden doors: the easiest fit.

Wood is soft enough to drill and chisel on site. Most smart locks are designed with wooden doors as the default. Standard Indian wooden doors are usually 32 to 40 mm thick, which falls inside the common range for smart locks. If your wooden door already has a cylindrical lock, some smart locks can reuse that hole with a retrofit model.

What to watch: cheap plywood doors. They look solid but the core is hollow or soft. A heavy smart lock can pull loose over time, especially in a rented flat where doors are not built for premium hardware.

Steel doors: needs a mortise lock.

Steel doors are common in apartments, main gates and many Indian society flats. You cannot simply drill a new hole the way you would with wood. Steel fights back, and a bad drill job ruins the door.

Most steel doors need a mortise smart lock, which sits inside a pocket cut into the door edge. If your steel door already has a mortise lock, the smart lock has to match that pocket size closely. Measure the existing mortise carefully before ordering.

What to watch: very thin steel doors under 35 mm. Some smart locks cannot clamp properly and the lock will feel loose. Also watch for fire rated doors, where drilling may void the rating. In that case, ask your building management before touching the door.

Glass doors: mostly no, sometimes yes.

This is where most people get disappointed. Standard smart locks are not made for glass doors. Glass cannot be drilled without a real risk of cracking, especially toughened glass, which can shatter entirely if drilled wrong.

Your options are limited but they exist:

• A rim lock that mounts on the door frame or on a metal patch fixed to the glass edge.
• A glass door lock designed specifically for frameless or framed glass doors.
• A frame mounted smart lock, where the locking mechanism sits on the wall or frame, not the glass.

What to watch: frameless glass doors with no frame at all. These are the hardest to fit. You usually need a specialist glass door lock, not a general smart lock.

Quick Fit Table

Screenshot this before you shop.

The Measurement Mistake Most People Make

Almost everyone measures the door width and height. Almost nobody measures the thickness or the existing cutout.

Here is what to actually do.

Take a ruler or a measuring tape. Measure the door thickness at the edge, near where the lock will sit. Write it down in millimetres.

Then look at the existing lock. If there is a round hole, measure its diameter. If there is a rectangular pocket, measure its height and width. If there is no existing lock at all, that is fine for wooden doors. It is a problem for steel doors, because you will need to cut a fresh mortise.

Now compare these numbers to the smart lock's specs. If the thickness is outside the range, stop. If the cutout does not match, stop. No amount of skill fixes a size mismatch.

If you want a broader look at choosing smart home hardware, browse the MR Homes smart lock collection. Smart locks start from around Rs 14,499.

Who Should Not Buy a Standard Smart Lock

• Frameless glass door owners. Standard smart locks will not fit. You need a specialist glass lock, not a general one.
• Very thin doors under 35 mm. The lock will not clamp properly and will loosen over time.
• Fire rated doors in apartment buildings. Drilling may void the fire rating. Check with building management first.
• Renters who cannot modify the door. Many smart locks need new holes. If your landlord will not allow drilling, look at retrofit models that reuse the existing hole instead.
• Anyone with a very old or warped wooden door. The lock may fit but the door will not close cleanly against it.
• Main gates exposed to heavy rain and dust. Not every smart lock is rated for outdoor use. Check the IP rating, which is the standard for water and dust resistance, before buying for an outdoor gate.

Common Questions

Can a smart lock be fitted on any door?

No. It depends on material, thickness and the existing cutout. Wooden doors in the 35 to 55 mm range are the easiest. Steel doors usually need a mortise model. Glass doors often cannot take a standard smart lock at all.

Can I install a smart lock on a steel door myself?

It is not recommended. Steel doors need precise mortise cutting, and mistakes are hard to fix. Use a professional installer. MR Homes customers often get installation guidance and a live video call demo to help plan the fitting.

Do smart locks work on glass doors?

Only with specialist glass door locks or frame mounted models. Standard smart locks are designed for solid doors and cannot be drilled into glass safely.

What door thickness does a smart lock need?

Most smart locks are built for doors between 35 mm and 55 mm thick [VERIFY by model]. Always confirm the exact range on the product page before ordering.

Can I use my old lock hole for a new smart lock?

Sometimes. Retrofit smart locks are designed to reuse an existing cylindrical hole. If your current lock is a mortise type, the new lock must match the mortise pocket size, which usually means a mortise smart lock.

Your Next Step

Measure your door thickness and check your existing lock cutout today. Write both numbers down. Then match them to the smart lock's specs before you order. If you are not sure which model suits your door, the MR Homes team is available 24/7 and can check the fit for you before you buy.