Isn’t it amazing? Throw out one thread, see where it lands, carry on from there and look what happens!
Many webs span gaps between objects which the spider could not cross by crawling. This is done by letting out a first fine adhesive thread to drift on the faintest breeze across a gap. When it sticks to a suitable surface at the far end, the spider will carefully walk along it and strengthen it with a second thread. This process is repeated until the thread is strong enough to support the rest of the web.
Credits to my seven-year-old grandson who spied this and shouted Grandma! you had better get over here right now and bring your camera!!