Using a pencil, divide and cut the plank into the following sized pieces: 40cm x 15cm (back), 23cm x 20cm (roof) and 23cm x 15cm (front). Finally cut a piece 20cm x 34cm and cut it diagonally to create two triangles for the sides of the bat box. Place the backboard on a flat surface and cut ridges into it, 2mm deep every 0.5cm, to make a 'ladder' for the bats to climb up.
Take one of the side triangles and measure 12.5cm from the acute angle along the longest length. Draw a horizontal line across the triangle at this point and cut off the smallest part. Repeat with the other side. Nail the two side panels to the front panel of the bat box. Sit the roof on top and push up the backboard to check for a tight fit. Nail on the backboard. Nail on the roof and an eyelet for hanging and hang above ground on a tree, post or house wall.