Washer-assembled screws Bolts or screws that incorporate a washer. Also called SEMS. As the washer is assembled beforehand, it helps increase work efficiency by eliminating the need to insert a washer and the problem of dropping the washer. It also prevents the user from forgetting to install the washer. Spring seat (spring washer) only, flat seat only, spring seat + flat seat, square, toothed type and the like are available.