A towel, it says, is about the most massively useful thing an interstellar hitchhiker can have. Partly it has great practical value.
wrap it round your head to ward off noxious fumes or avoid the gaze of the Ravenous Bugblatter Beast of Traal (such a mind-bogglingly stupid animal, it assumes that if you can't see it, it can't see you); you can wave your towel in emergencies as a distress signal, and of course dry yourself off with it if it still seems to be clean enough.
For some reason, if a strag (strag: non-hitch hiker) discovers that a hitch hiker has his 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. Furthermore, the strag will then happily lend the hitch hiker any of these or a dozen other items that the hitch hiker might accidentally 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 knows where his towel is, is clearly a man to be reckoned with.
Hence a phrase that has passed into hitchhiking slang, as in "Hey, you sass that hoopy Ford Prefect? There's a frood who really knows where his towel is." (Sass: know, be aware of, meet; hoopy: really together guy; frood: really amazingly together guy.)"
Douglas Adams, The Hitchhiker's Guide to the Galaxy
Idag är det Handduksdagen! Dagen man firar till minne av författaren Douglas Adams. Hur firar man? Jo man tar med sig en handduk, överallt!
Så ha en trevlig handduksdag och kom ihåg: Don't Panic!
Today I am celebrating Towel day. The day you are celebrating the memory of the author Douglas Adams. You celebrate by bringing a towel, everywere.
So bring a towel and remember: Don't Panic!