Maryland is the only Bay state where the legal hard crab changes size in the middle of the season. From April 1 through July 14 a male hard crab has to measure 5" point to point. On July 15 it becomes 5-1/4", and stays there through December. Peelers make the same jump, 3-1/4" to 3-1/2", on the same day.
Virginia and Delaware hold 5" all season. So if you fish both sides of the line, or you fish Maryland at all, your cull stick has two jobs a year.
The problem with a stick that's already short
The plastic cull sticks most supply houses sell are cut about a sixteenth under. That's deliberate. Crab shell wears the notch open, so the maker starts it short and lets it wear toward true. It works, roughly, for part of its life. Early on it passes shorts. Late, once the notch has worn past nominal, it throws back keepers.
On a 5-1/4" day a stick that reads 5-3/16" is passing crabs that are undersize by law. Natural Resources Police measure with a gauge, not your stick. The tolerance for undersized hard crabs in a bushel is not generous.
What we did about it
We machine ours from 5/8" solid 6061 aluminum bar and hold the gauge to .005". It reads 5-1/4" the day it lands and 5-1/4" two seasons later, because crab points don't chew aluminum the way they chew plastic. The same bar carries grading notches at 5-3/4" and 6", so you're sorting ones and maxes off the same stick you cull with.
It's listed at 5-1/4" because that's the Maryland late-season number and the one most of our customers need to trust. If you run a 5" measure, early season Maryland, Virginia, Delaware, call the shop and we'll cut it.
Check your stick on July 14
Whatever you run, put a caliper on it the night before the switch. If the 5-1/4" notch reads under, you're culling illegal crabs into the basket on July 15 and don't know it. If it reads over, you're throwing back money.
The full Maryland size and gear rules are on our regulations page, cited to COMAR. The stick itself is here.