Sea-weed! We were modern. We used balls. And issued them sometimes.
Observers needed them in fog on airfields ...... one of my lads was awol for a whole hour at dawn at Topcliffe and I had to do his job and mine [c. 1966] because he went to the enclosure for the 0600 big read of instruments and became disorientated. When he finally got back on the ATC runway check garry I issued him with string, ball, Banglestein's, observer for use of, unwinding behind. Loss of sense of humour.