Canvas is an extremely durable plain-woven fabric used for making sails, tents, marquees, backpacks, shelters, as a support for oil painting and for other items for which sturdiness is required, as well as in such fashion objects as handbags, electronic device cases, and shoes. It is popularly used by artists as a painting surface, typically stretched across a wooden frame. Modern canvas is usually made of cotton or linen, or sometimes polyvinyl chloride (PVC), although historically it was made from hemp. It differs from other heavy cotton fabrics, such as denim, in being plain weave rather than twill weave. Canvas comes in two basic types: plain and duck. The threads in duck canvas are more tightly woven. The term duck comes from the Dutch word for cloth, doek. In the United States, canvas is classified in two ways: by weight (ounces per square yard) and by a graded number system. The numbers run in reverse of the weight so a number 10 canvas is lighter than number 4. The word "canvas" is derived from the 13th century Anglo-French canevaz and the Old French canevas. Both may be derivatives of the Vulgar Latin cannapaceus for "made of hemp", originating from the Greek (cannabis). For painting Canvas has become the most common support medium for oil painting, replacing wooden panels. It was used from the 14th century in Italy, but only rarely. One of the earliest surviving oils on canvas is a French Madonna with angels from around 1410 in the Gemäldegalerie, Berlin. Its use in Saint George and the Dragon by Paolo Uccello in about 1470, and Sandro Botticelli's Birth of Venus in the 1480s was still unusual for the period. Large paintings for country houses were apparently more likely to be on canvas, and are perhaps less likely to have survived. It was a good deal cheaper than a panel painting, and may sometime indicate a painting regarded as less important. In the Uccello, the armour does not use silver leaf, as other of his paintings do (and the colour therefore remains undegraded). Another common category of paintings on lighter cloth such as linen was in distemper or glue, often used for banners to be carried in procession. This is a less durable medium, and surviving examples such as Dirk Bouts' Entombment, in distemper on linen (1450s, National Gallery) are rare, and often rather faded in appearance. Panel painting remained