Roll After Dark

Anal play

Anything at or in the anus — a plug, beads, fingers, a toy, or sex.

Why people do it
Dense nerve endings, and for many men the prostate. It is also a threshold: for a lot of people the significance of having agreed to it is a large part of what it does.
Smallest way in
One finger, plenty of lube, no schedule, and stop at the first "no". A small plug, worn for ten minutes, is the second evening rather than the first.
What to watch
Lube is not optional and silicone lube on silicone toys degrades them — water-based for anything inserted. Anything that goes in the ass has a flared base, without exception. Nothing goes from the ass to the cunt or the mouth without being washed. Go slowly: the tissue tears rather than stretching when it is rushed.
In the planner
29 different things carry this tag, and switching it off removes every one of them. The mildest of them sits at easy.