A "Rain Check" is basically a piece of paper allowing you to purchase a sale item at a later date because the store has run short of supply.
A typical rain check is dated and has an expiry date (maybe weeks or month), quantity of the item you want to purchase, a size, brand and store where it the rain check is valid. It will also have a signature from a department or store manager, or other authorized employee.
Metro runs a sale on chicken leg 1/4's for $1.49/lb. They run out of the chicken and offer rain checks to customers who ask for them.
The rain check will only be valid at Metro, by the expiry date, on the exact item and for the exact quantity specified. You cannot purchase chicken at the sale price (after the sale is over) without your rain check. You will have to give Metro the rain check, you can only use it once; even if you only buy 3 items and the rain check said you can have 6. All 6 must be purchased at the same time. You cannot exceed the 6 (example) that is specified on the rain check, you can only have the maximum.
Some stores have an idea when the "truck will be in" with the next shipment, while other stores may offer just a general "sometime next week." Either way, the rain check will be good for a length of time, just don't forget to use it!
There are the few stores in our midst that do not issue a rain check for items in their stores. This is inconvenient for the customer and frustrating. It's just their policy. The only thing you can do (besides not going back to check) is to ask when they expect a new shipment with your desired sale items on it to arrive.
Can I Use A Coupon With A Rain Check?
Yes. A coupon and rain check are two very different pieces of paper. One is a discounted price for a specific item that is kept until you are ready to redeem it. The other is a piece of paper entitling you to a sale priced item that the store ran short of during their sale. There is no reason that a rain check and coupon can't be used together.