At one time I had the Krueger snake trap on my predator controls page (Nestboxbuilder.com), but I wound up removing it because of all the inherent problems with it. That trap can kill the snake if left for too long, and if the snake is alive, well…I wouldn’t want to try and release a really ticked off snake from that trap, especially if it’s venomous….
One of my customers was having trouble with a snake raiding an open Phoebe nestbox, and we kicked around some ideas, but she finally found what looks to me a really humane and effective snake trap. Here ’tis:
http://www.backyardchickens.com/t/515899/best-way-ive-found-yet-to-deal-with-snake-problems