Preacher Curl Bench

How to adjust

Set the seat height so your armpits rest just over the top edge of the angled pad.
Adjust the pad angle if the bench allows it.

Sit with the backs of your upper arms flat against the angled pad, gripping the bar/dumbbell with arms extended.
Curl the weight up toward your shoulders, pausing briefly at the top.
Lower under control until the arms are extended but not locked out hard against the pad.

Keep the upper arms pressed against the pad throughout to avoid hyperextending the elbow at the bottom of the stretch.
If you run out of strength mid-set, don't let the arms snap straight: lower under control until they are nearly extended, set the bar onto the rack in front of the bench (or hand it to a spotter), then lift your arms off the pad and stand up.
Do not let the weight free-fall at the bottom.
Use a lighter load or a spotter near failure, since the fixed arm position makes it hard to bail out.