Metal shelf and utility carts are more rugged and can hold heavier loads than plastic shelf and utility carts. These wheeled carts are used to organize, transport, and store items, and they have open metal shelves that allow items to be efficiently loaded and unloaded onto or off of them. Low-profile carts minimize the distance that bulky or heavy items have to be lifted to put them onto the cart. Flow-through carts have openings that let dust and debris fall through their shelves. Order-picking carts have a document surface for tasks like note-taking and inventory. Instrument carts have shock-absorbing casters and cushioned nonslip shelves that protect items on the cart from shock damage and keep them from sliding around on the cart. Vertical-access carts have a built-in ladder for reaching high areas.