Throw down a c-note and say "50-50" or "Half" that usually means $50 in $1's and $50 in $5's. Lots of 3-6 players tend to favor this term.

Throw down 2 c-notes and say "Rack and a Stack" - Rack of $1's and stack (barrel is our term) of $5's.

Most of the time people refer to the chip color - In Iowa our $1 chips are white. So most people will say "Rack of White","Rack of Red" or "2 Stack of White, 1 Stack of Red"