______ are used to lift the work piece off the bottom of the vice.

Parallels are tools designed to provide a level and stable platform for workpieces during machining processes, particularly in milling or machining operations. They are often placed between the workpiece and the vice to lift the workpiece off the bottom, ensuring that it is held securely in a way that allows for accurate cutting or milling without interference from the vice jaws. This elevation of the workpiece also promotes better chip removal and enhances tool clearance, which can be critical for achieving high-quality finishes and precise dimensions.

Using parallels ensures that the workpiece is adequately supported throughout the machining operation and helps in maintaining alignment, which is crucial for producing parts to desired specifications. In contrast, the other options serve different purposes: shims are typically used for leveling or adjusting heights in assemblies, jigs guide the workpiece for consistent machining, and clamps secure the workpiece but do not provide the necessary elevation from the vice.