Swivel-Lock Carpet Stretcher has the benefits of both straight and swivel-head in one. The head has a 60° range of swivel for stretching patterned carpet. By unlocking the built-in lock pin, you can lock the swivel in 5 positions. Lock in a straight position for square stretching, or at 15° for angle stretching. The 30° setting is for extreme angles found in “L” shaped living/dining rooms. Adjustable locking lever for partial stretches. The pin depth adjustment bar has variable pin depth penetration for carpet thicknesses. Crain 520 Carpet Stretcher Parts List.