A detailed explanation of the art and science of dimensioning for existing or aspiring designers.Most creators of technical drawings do notappear to understand the basic principles ofdimensioning, nor do they understand exactlywhat the tolerances collectively will or will notdo. Equally, inside the workshop few trainedand experienced engineers have a similarunderstanding. .The reason is that the subject is not taughtin Universities, Technical Colleges, orWorkshop Technology books, and where it is, itis done badly, as the people doing the teachingare themselves in ignorance. This work is anattempt to help designers and engineersimprove their drawing standards. .