Inserting an object, either a drug or otherwise into ones rectum for a desired effect.
Shelving is generally done with pills for its high absorption rate, but causes serve anal irritation and can lead to further problems such as shitting bricks if a hallucinogen is taken.
My brother said his dad was going over to his girlfriend's house (at 10pm) to help build some stuff she purchased from Home Depot. I said "hmmm, hanging shelves, huh??"