An employee was resting his left hand on the edge of a roll-over fixture as he used a 2.5-pound "dead-blow hammer" with his right hand to level a cylinder head on the fixture in the salvage drill bed. When he raised the hammer, it struck something above and deflected down onto his left middle finger. He sustained a partial fingertip amputation, losing his fingernail and fleshy fingertip; there was no bone damage.