One end of the skip sometimes has a large door that hinges down to allow manual loading and unloading, these skips are called 'drop-door skips'. Skips are usually durable and tough, made to withstand rough use by tradespeople and labourers. The size of skip bins can vary greatly depending on their use, with sizes ranging from small 2-yard mini-skips to the very large 40-yard roll-on/roll-off skips. Even though these large bins can store many tonnes of waste, most lorries are limited to carrying around of material in the container.