1. Before planning the design of a tool, compare the cost of production of the work with present tools with the expected cost of production, using the tool to be made. Confirm that the cost of building jigs & fixture is not in excess of expected gain. 2. Before lying out the jigs & fixture decide upon the location point & outline a clamping arrangement. 3. Make all clamping & building devices as quick acting as possible. 4. In selecting the location points, see that two component part of a machine can be located from corresponding points & surfaces. 5. Make the jig 'fool-proof' that means design it in such way that work cannot be inserted except in the correct way. 6. For rough casting, make some of the locating points adjustable. 7. Locate clamps so that they will be in the best position to resist the pressure of cutting tool when at work. 8. Wherever possible make all clamps, integral parts of jig or fixture. 9. Avoid complicated clamping arrangements which are liable to wear or get out of order 10. Place or clamps as nearly as possible opposite to some bearing point of the work to avoid springing. 11. Round all corners