The
Stich plate is a simple, mechanical device used in
rock climbing and associated sports, (e.g.
mountaineering). It is a
friction device used
to control the release of
rope whilst
belaying.
Stich plates are typically made of aluminium/aluminum as this
is a strong, yet lightweight, metal. They are a shaped like a disc and are
a few mm thick. They can be found in single-, and double-slotted versions,
(double-slotted versions have two, parallel slots to accomodate climbers
using twin ropes).
A Stich plate is used in conjunction with a karabiner to create a
path of variable friction for the climbing rope. A loop of rope is
passed through the slot in the plate and clipped into the karabiner,
(normally attached to a climber's harness). The friction created by this combination is controlled by the 'angle of attack' of the rope
releative to the front face of the Stich plate: rope entering perpendicular to the
slot experiences a relatively small amount of friction. Resistance
increases as the angle between the rope and the front of the plate is
reduced from a right-angle. Rope angle in this context refers to the
'dead' side of the rope in the Stich plate, (i.e. the end of the rope
NOT attached to the other climber - known as the 'live side').
Some Stich plates have a helical spring attached
to the back face of the plate. In 'normal' conditions, the spring helps keep the Stich
plate spaced from the karabiner allowing easy passage for the rope. The
spring is compressed when
the rope becomes 'loaded' and the plate 'locks' the rope.
Using the Stich plate, it is possible for the belayer to actually 'lock' the rope in the device, (useful in the case of a fall). Obviously, the usefulness of the Stich plate is somewhat dimished if the climber on the other end of the rope weighs twice as much as you and you aren't safely anchored the nearest tree or boulder.
Safety Note: This description is for illustrative purposes only and is not a substitute for correct training!