Iron doors and gates are everywhere in north India. The grill door in front of the wooden main door, the shutter of a shop, the double gate of a kothi, the back door that opens to the service lane. They are strong, they are affordable, and they make a house feel safe.

They also eat cheap locks for breakfast. Rain, dust, heat and the constant banging of a heavy metal leaf wear out a lock on an iron door much faster than one on a bedroom door. So picking a lock for iron door use deserves its own thinking.

Why metal doors are harder on locks

A wooden door absorbs some of the shock when it closes. An iron door does not. Every slam goes straight into the lock and the keeper. Over months, that loosens screws and misaligns the bolt.

Iron also expands in summer heat and contracts on winter nights. A bolt that slides perfectly in October may jam in May. And of course, iron rusts, and rust spreads from the frame into anything fixed to it.

None of this means iron doors are a bad idea. It just means the lock has to be chosen for the job.

Lock types that suit iron doors

The aldrop with a padlock is still the most common setup on iron gates and grill doors, and it is popular for good reasons. There is very little inside it to rust or jam, and it can be welded or bolted firmly to the frame.

For an iron door used many times a day, a mortise lock fitted inside a box section works well, as long as the section is deep enough to hold the lock body. It gives you a handle for daily use and a key for night, without a padlock dangling from the door.

Rim locks and surface mounted locks are another option when the frame has no room for a mortise pocket. They are easier to fit and to replace.

For a double door iron gate, many families combine an aldrop in the middle with tower bolts at the top and bottom of the fixed leaf. The tower bolts stop the fixed leaf from moving, and the aldrop locks the two leaves together. It is simple and very hard to force.