off the rack

adjective

1. (of clothing) not made to specific or individual requirements; ready-made: off-the-rack men’s suits.
2. Slang. off-the-wall.

Ready-made, as in She has all her clothes made; she never buys a dress off the rack. The rack here is a frame from which clothes are hung. [Mid-1900s] A British synonym is off the peg, similarly alluding to a knob from which clothes are hung and dating from the late 1800s. Also see off the shelf.