Clamping is any activity where a clamp, clip, or peg is used to pinch or squeeze some portion of the anatomy.
Where clamps can be attached
Generally, for a part of the body to be considered for clamping there needs to be a certain amount of loose flesh which can be bunched up and pressed between the two arms or fingers of the clamp or peg.
Common body parts include:
Less common, but still effective body geography which can be considered include:
Removing a clamp or peg
Once a clamp or peg has been in place for a while, removing it can be a painful experience. The skin becomes sensitive and tends to "stick" to the clamp or peg as it is remove.
For some aficionados, this leads to something called zipping. This is where a line of pegs are clamped in a long row or flowing design (often to the belly or possibly the inner thighs), with a single thread of string passing through each peg. When the string is tugged, the pegs are pulled off in rapid succession (hence "zipping"). Thus there isn't just the brief pain of one peg being removed, but a whole series scoring a line or pattern on the bottom or submissive.
While the pain involved in having one or more pegs/clamps applied and later removed is an obvious and significant penetration, it's important to remember that this activity requires a lot of manual handling by the top or dominant. Thus, the actual physical contact by the top/dominant can be a significant penetration of the bottom/submissive.
The act of clamping or pegging tends to squeeze the blood supply out of the affected area. For this reason clamping or pegging for any significant length of time is inadvisable as it can lead to nerve damage or tissue death. Exactly how long is "safe" will vary from person to person and depend on how much flesh is affected and how tight the clamps or pegs are.