When a watch will go in one position and stop in another, the fault can generally be traced to a defective pivot or pivot-hole; thus, if the watch be held so that the balance works on one pivot or in one pivot-hole, and the watch stops, that pivot or hole is probably damaged. The pivot may be bent, its end may be bruised and resemble a " mushroom," or it may be too short to come through the jewel-hole and touch the endstone. The jewel-hole or endstone may be cracked. Other causes may be too much endshake to the balance; the balance arms may touch the index curl) pins or the hairspring stud; the balance rim may touch the balance cock or the watch-plate, or (in a Geneva) the centre wheel; the hairspring may not be flat, and may touch the balance arms or the balance cock; the lever may touch the roller, or the 'scape wheel may touch the top or bottom of the slot in the cylinder.