A towel is about the most massively useful thing an instersteller hitchhiker can have. Party it has great practical value, but more importantly, a towel have immense psychological value. For some reason, if a strag (strag: non-hitchhiker) discovers that a hitchhiker has a towel with him, he will automatically assume that he is also in possession of a toothbrush, face flannel, soap, tin of biscuits, flask, compass, map, ball of string, gnat spray, wet weather gear, space suit etc., etc.
Futhermore, the strag will then happily lend the hitchhiker any of these or a dozen other items that the hitch hiker might have "lost". What the strag will think is that any man who can hitch the length and breadth of the galaxy, rough it, slum it, struggle against terrible odds, win through, and still know where his towel is, is a man to be reckoned with.
