Silk is also used for the safety lines many spiders dragbehind them, which save them if they fall.
蛛丝也是许多蜘蛛拖在身后的安全索，能在它们跌落时保住小命。
2
He was barely able to drag his poisoned leg behind him.
他勉强拖着中了毒的腿向前走。
《柯林斯英汉双解大词典》
3
Since the lower regions of the cable are moving slower than the higher ones, a rising car will lag behind the orbiting anchor, causing a drag on the cable that could destabilize the entire assembly.