Bolts of fabric.
A bolt is a unit of measurement used as an industry standard for a variety of materials from wood to canvas, typically materials stored in a roll. The length is usually either 40 or 100 yards, but varies depending on the fabric being referred to, for example, a bolt of canvas is traditionally 39 yards. The width of a bolt is usually 45 or 60 inches, but widths may include 35–36”, 39”, 41”, 44–45”, 50”, 52–54", 58–60” and 66”, 72", 96", and 108". Original public domain image from Flickr