How to fit your own letterbox

How to fit a DIY letterbox

Fitting a letterbox is simple and easy, and doing it yourself will save you the expense of a handyman.

Here’s our step-by-step guide for your one stop mailbox come draft excluder.


Step 1

First of all, you’ll need to measure your door correctly. Working from the outside, measure the depth of the cross rail. Then make a pencil mark at the mid-point in two places, about 35mm apart, and 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 have already made. Centre your letterbox over the meeting point of the lines and mark the position of the fixing bolts on either side.

Step 2

Drilling holes for a DIY letterbox
© B&Q

Continue by drilling clearance holes for the fixing bolts. Try to make them slightly larger than the diameter of the bolt shank – normally about 6mm.

Step 3

Measuring a DIY letterbox opening
© B&Q

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.

Step 4

Preparing your DIY letterbox for a padsaw
© B&Q

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 padsaw or jigsaw – normally about 8mm.

Step 5

Using a padsaw to cut your DIY letterbox
© B&Q

Put the blade of a padsaw or power jigsaw into one of the corner holes, and carefully cut around the rectangle all the way through the door.

Step 6

Chiselling recesses for a letterbox hinge pin
© B&Q

After you’ve cut the opening, use a narrow chisel and mallet to cut recesses for the hinge-pin.

Clean out the corners of the opening and smooth the edges with sand paper.

Step 7

Fixing your DIY letterbox into position
© B&Q

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.


Trick of the trade

If your front door directly faces the elements, it’s a good idea to put a slight slope on the cut you make through the door, so that the opening on the outside of the door is ever so slightly smaller than the one on the inside. This way, any water droplets that find their way behind the outside of the letterbox won’t run to the inside and through onto the floor.

If you do this, you will need to ensure that the inside cover still fits over the opening well enough to get post through, so don’t make it too small.