Figure 4 Shows the (a) isometric projection and (b) isometric drawing (or view) of a cuboid.

While drawing isometric projection, an Isometric scale is to be constructed for convenience and all the measurements are to be taken from  this scale. As shown in figure 5, isometric scale is produced by positioning a regular scale at 45 ° to the horizontal and projecting lines vertically to a 30° line.

Figure 5.  illustrates the construction of an isometric scale.

                            i.e.  isometric length = 82% (approximately)