straightedge

Draw one through the original nail hole using a straightedge or level.

Six years later the astronomer Edmund Gunter had the bright idea of marking numbers on a straightedge proportional to their logarithms.

He began by describing age-old quests for solutions—using algebraic tools or straightedge and compass, which he considered rudimentary forms of computation.

The first requisite for this is a straightedge of iron or brass, as true as possible.

It is necessary also that the straightedge be applied frequently.

The cutter is guided along the straightedge as shown in Fig. 1.

The straightedge and the compasses are the only two drawing instruments recognized in elementary geometry.

In other words, the trisection of any angle, by the use of the straightedge and compasses alone, is impossible.