Lines on which you will find the ends of this puzzle's theme entries

Usage examples of diagonals.

From these draw lines to point of sight, then by their aid and the two diagonals proceed to construct the pentagon in the same way that we did the triangles and other figures.

The chief thing to be noted is the way in which the diagonals are produced beyond the square of the walls, to give the width of the eaves, according to their position.

Then by the diagonals and measurements on base draw the second step and the square inside it on which to stand the foot of the cross.

As she climbed she had to duck under cobwebs draped from the great dusty diagonals of the massive beams supporting the ceilings and the thick, white-plastered outer walls.