잠그다 + 아/어요 => 잠가요 잠가 or 잠갔다 is correct Some Korean people say 잠궈, 잠궜다 잠궈, 잠궜다 is not correct. It is from 잠구다. 잠구다 is a dialect of 잠그다 잠구다 + 아/어요 => 잠궈요