Traps

Animal Traps
Animal traps must be touching grass on four sides, and one of those must also touch grass. One of the Bait types needs to be placed in the left slot. Periodically one bait will be consumed and a potential drop for its type generated into the inventory. Animal traps cannot be automated with Hoppers - hoppers won't interact with the top or sides, and will pull bait out of the bottom.

Fish Traps
Fish traps only need to be touching water on four sides.