Sleeve (construction)

In construction, a sleeve is used both by the electrical and mechanical trades to create a penetration in a solid wall, ceilling or floor.

Sleeves can be made of:

Steel sleeve used to create a pipe penetration , with uneven rockwool packing , making an incomplete firestop .
Notice the sleeves , fastened to the timber forms before the concrete is cast.
improper sleeving in a drywall assembly.