The way you fit both a letterbox and a cat flap is broadly similar. Both are fairly straightforward jobs, but do make sure you follow the instructions carefully and double-check all the measurements before you make the first cut.
How to measure your door for a letterbox
Letterboxes come in a range of designs and materials. Some have a handle incorporated that doubles as a door-knocker. You could also decide to fit an internal flap cover on the inside of the door, which reduces draughts and looks neater.
If you're using solid brass screws (which are relatively soft) you'll need to drill full-length pilot holes. But don't use a power screwdriver, as you might damage the screw slot.
Working from the outside of your door, measure the depth of the cross rail. Then make a pencil mark at the mid-point in two places, about 35mm apart.
Draw a straight line between the two marks.
Next, measure the width of the cross rail and find the centre point. Draw a short vertical line across the one you've already made.
Centre your letterbox over the meeting point of the lines, and mark the position of the fixing bolts on either side.
How to fit a letterbox
You'll find this job is much quicker and easier if you use a power jigsaw to cut the opening for your letterbox.
One Planet Home - Sealing out draughts
It's easy to fit a cover over your interior letterbox opening to keep draughts out - and your hallway cosy.
Start by drilling clearance holes for the fixing bolts. Try to make them slightly larger than the diameter of the bolt shank - normally about 6mm.
With a pencil, mark where you'll need to cut the opening. It should be a fraction larger than the hinged part of your letterbox
Drill a hole at each corner of the slot. You'll need to use a drill bit that's large enough to create a hole into which you can put the blade of a pad saw or power jigsaw (normally about 8mm).
Put the blade of a pad saw or power jigsaw into one of the corner holes, and carefully cut around the rectangle all the way through the door.
After you've cut the opening, use a narrow chisel and mallet to cut recesses for the hinge-pin. Next, clean out the corners of the opening and smooth the edges with abrasive paper.
Fit the letterbox into position using the nuts supplied. If the bolts are longer than the thickness of your door, just shorten them with a hacksaw.
How to fit a cat flap
There are lots of different types of pet door on the market. Most of them have a simple locking mechanism, although some more sophisticated versions have a remote-controlled door that's operated by the collar your cat wears. They should all come with a full set of fixing instructions, which you'll need to read carefully before you start work.
First, you'll need to decide where to put your cat flap. Take into account how easy it is to fit, and how your cat will use it. Stick the template supplied with your cat flap to the door with adhesive tape. Check it's level, and drill through the four points shown on the template. The holes need to be big enough to insert the blade of a pad saw or jigsaw (normally about 8mm).
Take the template off and, using a ruler, draw lines between the four holes.
Use a pad saw or power jigsaw to cut through the door along the lines you've made. Push out the piece and smooth the edges with medium-grade abrasive paper.
Hold the cat flap in position, lined up with the hole. Check it's level and drill clearance holes for the screws.
Hold both sides in place through the open flap and screw them together, fixing each screw through the clearance holes. Then check the flap can swing freely.