not be true. The assumption can result in expensive and
time-consuming rework. Play it safe and read the
dimensions shown on the drawing.
Legend or Symbols
The legend, if used, is generally placed in the upper
right-hand comer of a blueprint below the revision
block. The legend is used to explain or define a symbol
or special mark placed on a blueprint. A symbol may
have more than one meaning. It should be noted that all
symbols used are not from a single standard. The
important thing is that you understand the meaning of
the symbols on the drawing on which you are working.
The legend will give you that meaning. The legend in
figure 2-3 shows the symbols and their meanings from
the partial floor plan below it.
Bill of Material
On a blueprint, the bill of material block contains a
list of the parts and material used on or required by the
The block identifies parts and
materials by stock number or other appropriate number
and also lists the quantity used or required.
The bill of material often contains a list of standard
parts, known as a parts list or schedule. Many
commonly used items, such as machine bolts, screws,
fittings, and valves, have been standardized by the
Figure 2-3.A legend with partial floor plan.