The ones you need to worry about are the 330 Conibear traps, they have a 10" x 10" opening and are used primarily for beavers. By law, I believe they're supposed to be 3/4 submerged in water. "Most" trappers abide by the law, the problem is, water levels can fluctuate drastically in a short period of time; ex a beaver dam is opened or blown open, thus leaving these deadly traps completely out of the water. They are not easily seen, but they are generally set in areas where beavers are, which is pretty much near any water source, especially in the spring. If you do see one out of the water, set it off by throwing a stick against the trigger. I trapped as a teenager and placed them in beaver runs going into a house, runs leading towards food sources on higher land, near dams, culverts, etc. Unfortunately, if your dog gets into one of these, it's most likely game over very quickly, as they can kill a 65 lb beaver in the blink of an eye. Check out the conibear HSOforum for instructions. Basically, you need to compress each of the two springs and hook them closed with the safety latch attached to the spring. They are normally set with a scissor type tool because of the difficulty doing so by hand, in a jamb you would hold it up and compress the spring by foot. Hope this helps.