The tight reg who open-limps has a hand he doesn't want to play for a raise. Small pairs, suited connectors, suited aces. He's not trapping - he just doesn't know how to build pots with speculative hands.

Why they do it

Tight regs raise their strong hands. When they limp it's because they want a cheap flop with something they're not confident playing big. Isolate them and c-bet boards that miss small pairs and connectors - which is most boards.

The adjustment

Raise them from late position, 4-5x. Take it preflop or fire one c-bet. They'll fold quietly and wait for the next one.

What it's worth

Do this three times a session and you've added a meaningful chunk to your win rate without ever going to showdown.