A commercial crab pot is a simple machine with about a dozen parts, and every one of them has a name, a spec, and in most states a regulation. Here is the whole pot, top to bottom, with what each part does and where the rules come in.
Wire
Hexagonal or square vinyl-coated wire mesh formed into a cube, usually 24" on a side for a Chesapeake pot. Mesh size matters legally: fine-mesh peeler pots are exempt from cull ring rules in several states, and Louisiana exempts pots built from 2-5/16" square mesh or larger. Coating extends life against salt; galvanized-only wire rusts out in a season or two.
Funnels (throats)
Inward-tapering wire cones on the sides of the lower chamber. Crabs climb in, can't find their way back out. Where terrapins are a concern, the funnel is where the excluder goes.
Turtle excluder / bycatch reduction device
A rigid rectangle fastened inside each funnel entrance, sized so a crab passes but a diamondback terrapin doesn't. Maryland, Delaware, New Jersey, New York and Florida each require them on some or all recreational pots, with dimensions from 1-3/4" x 4-3/4" to 2" x 6" depending on the state. See the regulations by state.
Bait box
A wire cylinder or box in the center of the lower chamber that holds bait behind mesh fine enough that crabs can smell it but not eat it. Some builders use a plastic bait box with a snap lid.
Divider (apron, baffle, stairs)
The inverted-V or sloped wire partition separating the lower bait chamber from the upper holding chamber. Crabs work upward through the gaps and stay up. Several states define cull ring placement relative to the divider: North Carolina wants one ring within a mesh of the divider corner, Louisiana wants two flush with the baffle.
Cull rings (escape rings)
Rigid rings set in the pot wall that let undersized crabs out. Required in ten of the thirteen blue crab states, in one of two sizes: 2-5/16" or 2-3/8", with Maryland and Virginia's seaside adding a 2-3/16". Count and placement are state-specific. Ours are 2-5/16", molded in Baltimore, and the state table says exactly where that size is legal.
Harvest door
A hinged wire panel, usually in the top, that opens to dump the catch. It's held shut by tension from a band and a hook, and it's the part of the pot you touch on every pull.
Door hooks
Molded plastic hooks with a cinch at one end for the band and a hook at the other that catches the door wire. Most commercial pots run two per door. The dimension that decides fit is center to center, cinch to hook. Ours are 4-1/4" overall, 3-1/2" center to center, cut with relief at the points so they lay flat under a stack and a radiused cinch so they don't crack. How to rig them.
Bands and bungee
Rubber crab pot bands or bungee cord anchored to the frame and run through the hook's cinch to hold the door closed. Rubber lasts longer and holds tension; bungee is cheaper and frays. Both work in our hook.
Biodegradable panel
A section of the pot secured with twine or light untreated wire that rots out if the pot is lost, so it stops fishing. Required in New Jersey, Florida and Texas with specific dimensions and materials. Many watermen add one everywhere; a lost pot that keeps killing crabs is a pot working against you.
Weights
Rebar or concrete along the bottom edge to hold the pot on the bottom in current. Not regulated, but a light pot walks and a walking pot gets lost.
Line and float
Non-floating line from the pot to a surface buoy. Every state specifies buoy size, color, and marking, from Alabama's orange with an "R" to Texas's striped white 6" cube, and most ban floating line and plastic bottles. The state pages have each one.
Zip ties and hog rings
What holds it all together. Rings and hooks install with hog rings or UV-rated zip ties, no tools beyond pliers.
Off the pot: the cull stick
Not on the pot, but you use it at every one. A bar with a notch at the legal width, bolted to the culling board, that tells you in one motion whether a crab stays. How to measure and grade. Ours is machined aluminum, held to .005", with grading notches on the same bar.
Building or rebuilding pots?
We mold the hooks and rings in Baltimore and sell them by the box, direct. Pot builders, start here. Dealers, here.