shelves
A shelf is a flat piece of wood, metal, or glass which is attached to a wall or to the sides of a cabinet. Shelves are used for keeping things on.
He took a book from the shelf.
他从那个架上拿了一本书。
off the shelf
If you buy something off the shelf, you buy something that is not specially made for you.
Lower-priced jewellery will be sold off the shelf by this autumn.
低价的珠宝到今年秋天就将现货出售。