Belgium Style Drop Trap
Pictured to the right is a four hole Belgium style drop trap which is most commonly used. It comes with a hinge on top, so you can release the birds through the same opening. Many fanciers including myself, use this style trap with the electronic timers. It seems to save time trapping birds in over the "bob style trap"
Four hole fits 10 1/2" X 17 1/8 opening