Fool Proofing is a method by which ensures that the workpiece will fit into the work holder only if the workpiece is placed in the correct position.
For fool proofing the design of jig and fixture is incorporated in such a way that it make it impossible to place the workpiece into incorrect positon but it will not interfere with loading and unloading of workpiece.
To attain perfection in machining fixture should attain the workpiece in only one position.
From the above image we can see that how jig and fixture is used to fool proof the drilling process. The three locating Pins fix the workpiece in a certain position and the workpiece will not fit if placed incorrectly. The clamp is used to hold the workpiece. Body, locating pins and clamp combines to make a fixture.
If a hole is to be made at point P using drilling , then the jig is used to guide the tool to the point P accurately and remove any chances of error in drilling.
In this way jig and fixture makes the drilling process fool proof.