The center joint of the crown tangents is shown to be square to tangents b and c. When these lines are projected into an oblique plane, the joints of the wreaths can be made to butt square by applying the bevel to them.
All handrail wreaths are assumed to rest on an oblique plane while ascending around a well-hole, either in connecting two flights or in connecting one flight to a landing, as the case may be.
In the simplest cases of construction, the wreath rests on an inclined plane that inclines in one direction only, to either side of the well-hole; while in other cases it rests on a plane that inclines to two sides.
Fig. 84. Obtuse-Angle Plan.
[Fig. 87] illustrates what is meant by a plane inclining in one direction. It will be noticed that the lower part of the figure is a reproduction of the quadrant enclosed by the tangents a and b in [Fig. 86]. The quadrant, [Fig. 87], represents a central line of a wreath that is to ascend from the joint on the plan tangent a the height of h above the tangent b.
Fig. 85. Acute-Angle Plan.