1. A limestone rib formation that protrudes within the wall which can occasionally suit within the pinching grasp of a climber's hand. Other causes of weak playability are lousy spindle motors, when they're the comb geared tiny Mitsumi DC kinds, and (very) at times deposits to the outer surface area http://boulder-sewing-machine-re16036.dgbloggers.com/1891007/boulder-sewing-machine-repair-options