A trap is a small and subtle modification to the outline of a letterform, intended to compensate for optical aberration and ink bleed. The use of traps is often not necessary, but especially in a text face some degree of trapping helps preserve its integrity in small sizes and adverse output conditions. ¶In order to implement trapping quickly and consistently, The MicroFoundry has devised a device called the Trapping Flower. It is composed of concentric rings of variable diameter, the innermost two being the most important: the Aperture ring determines the size of the trap; the Minimum ring determines if a given corner needs to be trapped. The other rings are used for measurement.

The following four frames reveal the process. 1:The Trapping Flower is placed so that the Aperture ring abuts against the sides of the corner. If the corner is beyond the Minimum ring, it needs to be trapped. 2:Tangent points are placed where the Aperture ring touches the sides of the outline. 3:The distance from the Minimum ring to the corner is measured, and this number is tripled. The corner point is then moved to its new distance from the Minimum ring. 4:Control points are dragged out from the Tangent points, reaching the Minumum ring. ¶The parameters of the Trapping Flower (such as the multiplier in step 3) are variable. To be continued...