I recently used a tall baby food jar with a string attached to the top to catch a crab that hitchhiked on some live rock rubble. I put in a chunk of shrimp and set the jar sideways in front of his lair so he had easy access. I then waited . . . .waited . . . waited .. . . when the sucker was committed (all the way in the jar) I pulled the string and tipped the jar up so he could not climb the sidewalls. It took about an hour but the tentative crab who spent about 40 minutes trying to reach the shrimp without going all the way in the jar, like he knew it was a trap but couldn't resist the shrimp, made it fun.
Good luck