It partly depends on how many exercise prices are available because if there are more than two you are able to suggest more than one collar.
A borrower will buy a put option and sell a call option. The strike price for the call option will have to be higher than that for the put option (in order to fix both a maximum and a minimum effective interest rate).
A depositor will buy a call option and sell a put option.
Have you both watched my free lecture on interest rate options and collars (and read our free lecture notes on collars)?