What makes a good pellet trap and backstop?

A good pellet trap stops the projectile completely and quietly without ricochet.

Common designs are steel boxes lined with duct seal (ballistic putty) or a plastic tote filled with shredded rubber mulch behind a carpet face. Pellet traps are rated for an energy ceiling and a minimum standoff, often up to 20 ft-lbs at 10 meters or more. A backstop is the larger barrier behind the trap to catch missed shots; plywood, packed earth, or angled steel works. Inspect both regularly and replace the duct seal or rubber when pellets start piling up.