An assisting person is a third-party playing at an activity.
Assisting in corporal punishment
In BDSM play such as consensual spanking, an assisting person can assist in the preparation such as by helping to undress the spankee or getting ready needed objects, implements or furniture. While the punishment takes place, they can help hold the spankee in position or just stand nearby and watch. The assisting person can also, for example, manage the spankee during corner time, then place them in a new position for the next part of the punishment session. The presence of an assisting person may add to the humiliation and enhance the ritual of the scene.
The role, rank and status of an assistant
The assisting person can be a second top or another bottom. In either case, he or she will take a middle position in the power exchange.
Top Top Assistant top or || || Assistant bottom Bottom Bottom
The status of the assistant will determine how the top will address and instruct him or her. If the assisting person is another bottom, he or she will be submissive to the top in the scene and will take and execute orders. This scenario is often found in spanking studios where there is one dominatrix and several subs/slaves.
If the assisting person is another top (or potential top), he or she can be of about equal rank to the spanker. This scenario is often found in spanking stories and spanking videos. In this case, the assistant will not take orders, but will help on request. An intense emotion can arise (for the spankee, for bystanders, or the audience) when the spanker addresses his or her assistant in a particularly relaxed manner and in polite, friendly or affectionate words, which forms a stark contrast to how they both treat the third person who is about to be punished.
For example, if the spanker and the assisting person are (or play) a married couple (e.g. the spankee's parents), lines such as "Darling, could you please give me a hand?" or "Will you please hold up his hands, my dear?" can take great subliminal effect.