you watchj a bbike go past, note what brakes, forks and frame it has and then 10 minutes later get told it was being riden by a stunning leggy huge boobed gorgeous female... and you didn't notice!!!
when you use your 2 biggest fingers as a bike (first finger front wheel, 2nd finger rear) and ride your finger bike over your girlfriends tits without realising what your doing...
(and yes i've done both, there is no hope for me!!!)