A variety of machines are used in perforating stamps. One perforates
only a single row of holes at a time. This is known as the guillotine
machine because its action suggests that unpleasant instrument. Another
machine is called the comb machine because the needles are arranged to
perforate across the top of a row of stamps and at the same time between
the stamps of that row. This arrangement somewhat resembles a comb. It
will be seen that the first application perforates the stamps of one
row on three sides. The application of the machine to the next row below
completes the fourth side. In the best perforating machines the needles
are arranged in circles around a spindle. The sheets pass under this
roller and are perforated in one direction. A similar machine makes the
perforations in the other direction.

There is another form of separation called rouletting, from the French
"roulette", a little wheel, its simplest form being produced by a small
wheel with an edge of sharp points. By this process a series of small
cuts is made between the stamps but none of the paper is removed.

[Illustration: Rouletting, Large Gauge]

[Illustration: Rouletting, Small Gauge]

In these two illustrations are shown roulettes of large and small gauge.
The same result is also obtained by setting printers rules which have a
notched edge between the _clichés_ which compose the plate. These rules
are set a trifle higher than the _clichés_ so that, when the sheet of
paper is pressed against the plate in printing, the points of the rules
are forced through it. These points receive ink the same as other parts
of the surface of the plate and the effect thus produced is called