[Illustration: Supported and unsupported circles]
_The Design and the Process._--The purpose for which a mat is used
requires as one condition of design that there should be a plain
surface in the middle. If the general form be square the design at the
corners should be strengthened. If circular, the design should be so
arranged that it will lend support to the perfect curves of the circle
rather than weaken them. In the three outlines given below, C shows
a form supporting the circle; D and E show forms tending to weaken
the circle. Conditions determining size are more variable in this
problem than in others, because of the great variety of uses which a
mat may serve. In a design like that shown in A of the accompanying
illustration, the portions left untooled--_i. e._, the leaves and
fruit--may be raised still more by pressing out the leather from the
back by means of a tool. To do this the leather should be placed face
down in the palm of the hand or on modelling wax, which has been
covered with a piece of chamois or sheepskin. Then by gently forcing
the leather down with a round, blunt tool such as the blunt end of a
nut pick the desired relief in the figure may be obtained. After this
is done it will probably be necessary to turn the mat over and correct
the modelling. In order to preserve the higher relief it is well to
back it up with cotton batting, soaked in paste, and finally to cover
the entire back with a lining of silk or leather.
[Illustration: Two mat designs]