Carriage bolts are bolts with a flat head with a square underneath that is pulled or hammered into the wood or falls into a filed square in the metal to ensure that the carriage bolt does not rotate when the nut is tightened; that it is locked. For example, a carriage bolt can be used to secure something where the head of the bolt should not protrude, such as a piece of furniture, or where the thing must be able to be operated without tools, such as wing nuts on a leaf press. Carriage bolts are available in many diameters and in different materials.
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