Lobster traps were traditionally constructed out of wood but they are now usually plastic. An opening permits the lobster to enter a tunnel of netting. Pots are usually constructed in two parts, called the "chamber" or “kitchen”, where there is bait, and exits into the “parlour”, where it is trapped from escape.

Lobster pots are usually dropped to the sea floor about a dozen at a time, and are marked by a buoy so they can be picked up later.

The trap can consist of a wooden frame surrounded by a rope mesh. The majority of the newer traps found in the Northeast of the USA and the Canadian maritimes consist of a plastic-coated metal frame. A piece of bait, often fish or chum, is placed inside the trap, and the traps are dropped onto the sea floor. A long rope is attached to each trap, at the end of which is a plastic or styrofoam buoy that bears the owner's license number. The entrances to the traps are designed to be one-way entrances only. The traps are checked every other day by the fisherman and rebaited if necessary. One study indicated that lobster traps are very inefficient and allow almost all lobsters to escape. Yet, this inefficiency also allows younger lobsters to escape and breed, thus reducing the possibility of overfishing.

The same principle, though with different detailed design, is used also for catching animals such as crab, eels and wasps. The principle was also employed in the design of the non-spill ink well, used with dip pens.

The lobster trap was invented in Swampscott, Massachusetts in 1808 by Ebenezer Thorndike and revolutionized lobster harvesting.

An 1899 report by the United States Fish Commission on the Lobster Fishery Of Maine, described the local "lath pots" used by Maine lobster fishers: