2 options for automatic door latch

Instead of a regular lock, you can install an automatic latch on a gate, workshop door, garage or other room. It blocks the door when it is closed. This is a simple, fail-safe mechanism that cannot fail at all. Let's consider how you can make 2 such structures.

Materials:

Strip 40 mm or sheet steel 3-4 mm;
M12 bolts and nuts;
steel bar 10-12 mm.

Option 1. Latch on the door frame

The first option involves installing a bolt on the door frame. The counter part is placed on the door leaf. A rod is welded or otherwise secured to the door, which will be secured by the latch.

The valve itself is made of sheet steel or strip. It is installed on the door frame or wall opposite the counter. A bolt and nut are used to secure it. The valve extends from the box or wall so much that the mating rod can be placed between them.

A triangle-shaped flag with an elongated, rounded first corner is welded perpendicular to the valve.When the door is closed, the rod of the counter rests against it and lifts the latch, thereby moving behind it until it falls. At the bottom and at the top, limiters for its stroke are placed from rods. The edge of the latch is made beveled so that when it rises, it does not interfere with the door leaf closing.

This type of lock can only be opened from the inside. To do this from the outside, the valve should be equipped with a lever or cable to pry it upward.

Option 2. Latch on the door leaf

In this case, the latch is installed on the door leaf with a slight indentation. To limit its stroke, 2 lower stops are used. One does not allow it to fall, and the second, lowered at an angle, does not allow it to rise above the necessary level. It tends downward due to its own mass. The latch is provided with a hook to pry it upward with your finger.

The counter part in this version is made from strip. Its edge is ground at an angle and rounded. A cut is made on it, into which the latch can fall, thereby blocking the door.

Both types of automatic bolts provide very reliable closing of the door. They are easy to manufacture and absolutely trouble-free. Their maintenance is reduced only to periodic lubrication of the valve axis.