Abstract: A specimen slicing mechanism such as a microtome or an ultramicrotome in which a specimen is held by a specimen arm and is moved through a knife. The specimen arm is made of two segments which are secured to each other via a lockable hinge assembly. The lockable hinge assembly uses a hinge between the two segments as well as a locking mechanism. When locked, the two segments are in a fixed relationship which causes the specimen to be forced through the knife by the action of the motor. When the locking mechanism is unlocked, the segment of the specimen arm holding the specimen is able to rotate (“float”) around the hinge; thus allowing the specimen to be sliced by the knife as gravity pulls the segment downward.