Worship, service to a partner

Feet, boots, kisses on command, or saying whose body this is.

Why people do it

Feet, boots, kisses on command: the point is the posture, not the body part. It is submission expressed as attention, and it is one of the few things on this list that can go on for an hour without escalating.

Smallest way in

Ten minutes at the feet with a specific instruction — where, how, and for how long.

What to watch

Wash first, and check that neither of you has a cold sore or broken skin. Nothing else here to be careful of.

In the planner

10 different things carry this tag, and switching it off removes every one of them. The mildest of them sits at easy.