A spider web is made of silk. Spiders have spinneret glands. These glands produce the silk spiders use when they build their webs and are located on the abdomen, normally on the bottom. The silk is very light as needed for the wind to carry it. Spiders can make sticky and nonsticky silk. The spider knows how to use both to build the most sturdy web possible. Spiders are careful when constructing webs to make it possible to stay on the parts that are not sticky to prevent themselves from becoming glued to their own web. Amazing creatures!