[header] How to build a simple birdhouse [title] Cut the wood to the sizes needed. [step] Cut out 7-9 6x6 pieces of wood, measuring 2 cm-5 cm thick and thin, depending on your intended size. These form the 4 walls, the 1 floor and the 2 roof pieces. 
[title] Using a compass, draw a circle on one of the squares. [step] Depending on the bird you're hoping to encourage to stay, the circle should be of the size it can adequately fit into.