Knitted fabrics are made from interlocking loops of yarn. There are two main types of knitting: weft knits and warp knits. In weft knitting, loops are linked across the width, while in warp knitting loops are linked vertically. Weft knits can be made by hand or machine and have stretch and retain heat, but can lose shape. Warp knits are made quickly by machine, are elastic but hold their shape, and lie flat when cut.