Door security bolts, or rack bolts as they are sometimes known, are very effective and relatively inexpensive. They are a popular form of door and window security being much stronger than the ordinary surface mounted bolt with the added bonus of being discreet. Fit them on all external doors including the patio door, generally at the top and bottom.
The 'key' to the bolt is a ridged cylinder that, when turned in the lock on the face of the door, causes a ratchet to force the bolt into the door frame. Without this key, the bolt cannot be turned.
Marking the drilling holes
With a pencil, make a central mark on the edge of the door to indicate the positioning of the bolt. Using a try square and pencil, draw a line around to the inside face of the door. Some manufacturers include a paper template with the security bolt to help with this.
Drilling the first hole
Drill a hole into the edge of the door to the depth of the bolt keeping the drill straight and level. An easy way to judge the depth is by measuring the bolt and putting some masking tape on the drill bit at the same length.
Cutting the recess
The faceplate needs to be attached flush with the door's edge so a shallow recess must be made to accommodate it. To do this, push the bolt into the drilled hole so that the faceplate itself will act as a template - make a pencil mark around it. Remove the bolt and faceplate and using a chisel cut the shallow recess.
Now, holding the bolt flush with the face of the door, use the drawn line as a guide and make a pencil mark to denote the keyhole. Drill a hole on this mark deep enough to allow the key, when inserted, to engage the bolt. Test the hole's accuracy by slotting the bolt in place to see if the key operates the bolt correctly. You may have to drill slightly deeper. If all is well, screw the faceplate in place on the edge of the door and attach the key faceplate to the face of the door.
The door jamb
An engagement hole needs to be drilled in the door jamb to accept the bolt. If you have a small piece of carbon paper, close the door with the paper trapped, screw the bolt against the jamb and the carbon paper should leave an accurate mark showing where to drill. If no paper is to hand, close the door and wind the bolt in and out a few times which should leave a faint impression as an indicator. Open the door and drill an appropriate sized hole at the mark. Confirm that the bolt slides smoothly into the hole. Using the cover plate as a template, draw around it as a guide. Cut a shallow recess and screw the cover plate in place.