:slap on the side: n. (also called a {sidecar}, or abbreviated
`SOTS'.) A type of external expansion hardware marketed by
computer manufacturers (e.g., Commodore for the Amiga 500/1000
series and IBM for the hideous failure called `PCjr'). Various
SOTS boxes provided necessities such as memory, hard drive
controllers, and conventional expansion slots.
-- The AI Hackers Dictionary