WORKING DRAWINGS HANDBOOK, Fourth Edition

Working Drawings Handbook

serve as a template for the opening, the architect will be
faced with making the brick opening larger all round than
the overall dimensions of the frame which is to be fitted
into it; for otherwise it will be impossible, in practical
terms, to insert the one into the other. It would seem that
the joiner will need to work to one set of dimensions and
the bricklayer to another if a satisfactory fit is to be
achieved. How, simply, is each to be instructed?

To answer ‘dimension the frame 15 mm all round smaller
than the opening’ is unduly simplistic. Apart from the

daunting prospect of trying to represent a series of

15 mm differences on a general arrangement plan at a

scale of 1:100, the problem is compounded by

inaccuracies which are bound to occur in both the

fabrication of the frames and the erection of the

brickwork, to say nothing of the difficulty of inserting one

centrally into the other.

The solution lies in the concept of the coordinating

dimension, which may be defined as the distance

between two hypothetical planes of reference—known

4.9 The conventions shown are contained in computer software and may be selected as
required for the drawing being undertaken. (Reproduced by courtesy of Autodesk Ltd)