The chief desiderata in designing a satisfactory Pise plant appear to be
these:
All constituent parts should be reasonably light and easy to handle. The
shutters should be rigid and not liable to warp, without being
expensively constructed. The shutters, when clamped in position, should
be firmly and positively supported, without deviation from the vertical.
The fairway between the shutters must be as little obstructed by the
cross-braces as may be, leaving good room for the men on the wall to
tread and ram.
The through-pins by which the shuttering rests upon the base wall or on
a completed course of Pise, must be easily withdrawn without injury to
the wall.
The shuttering must be easily disengaged and removed from the wall, one
side at a time.
The special corner-piece must have some means of rigid attachment to the
ordinary shutters on the two meeting walls.
There must be some means of blocking off the shuttering at any desired
point, for the forming of door or window openings at any level.
The whole apparatus must be as simple and as fool-proof as possible, and
built to stand rough usage and exposure to the weather.