First you need to choose a lock and read its instructions. Locks are overhead, mortise, mortise latches with handles - keys. Usually, the lock is cut at a height of 90 - 110 cm from the floor.
As a rule, overhead locks are installed on the entrance doors. Fastened with screws on the inner surface of the door leaf and door trim. First of all, a hole is made with a drill and a chisel for the lock rod. Then the lock is applied to the marked place, the location of its front bar at the end of the door is designated, and with the help of a chisel, a recess is made under it - a "nest". Then the lock is again applied to the door and marks are made with a pencil for the screws. The strip should not protrude beyond the surface of the door end.
Having secured the lock, the door is closed, the position of the locking box is marked and it is also fastened with screws.
Mortise locks are most often installed together with a handle with a key hole. The lock cuts into the end of the door trim. When cutting into a paneled door leaf, the lock must not be cut in front of the middle beam of the jamb, as the hole will loosen the spike connection of the door.
To begin with, the place of the lock insert is marked. The contours of the lock, applied with the end side to the harness, are circled with a pencil, with the help of an awl, mark the keyhole.
Then transfer the placement of the lock to the side of the strapping and mark the thickness of the lock with a pencil along its axis. From the end of the door along the marked contour, holes are drilled with a depth along the length of the lock and a chisel is made to make a recess along its contour. After that, the lock is tried on, the contour of the end of the lock is drawn and a recess is made so that it is flush with the door frame.
In order to mark the installation location of the strip located on the door frame, the door is closed. A notch is made at the mark for the bolt or latch bar.
To mark the recess for the lock bolt, rub the butt of the bolt with chalk or whitewash, close the door and carefully turn the key. Thus, a place for the nest is marked.
Another way is to thinly smear the door frame opposite the bolt with a layer of plasticine and push the bolt with the key. The imprint left from it will be the place of the hole for the strike plate.
The bolt hole can also be determined using a sheet of paper: a quadrangle is cut out according to the size of the area of the crossbar end, one side of which is moistened with water and gently glued to the crossbar end, and glue is applied to the other. After they close the door, turn the key, thus pressing the bolt to the door frame. The paper adheres to the jamb and indicates the location of the hole.
Mortise latches, equipped with dowel handles, are attached in this way: they mark the place of installation of the handle, then select a tree under the latch body with a drill and a chisel, and drill a hole for the rod to which the handles with strips are attached. The latch is inserted into the slot and secured. After that, a rod is inserted into the latch body, then a handle with strips. The structure is fixed with screws. To ensure the softness and soundlessness of the handles, the latches are lubricated with petroleum jelly or oil.