What's common between a helmet and a birth-control device ?

For starters, both helmet and condoms have been invented to save lives, the former by saving
your head (and life) incase of accidents, while the latter could save you from STDs like AIDS.
But this topic was inspired by my friend headers (not real name, but his id on team-bhp), whose current signature on the forum reads as :

Wearing a helmet is like using a condom. Unless you know how to use it, it is useless !!!
HELMET - Strap up for safety !!!

So, you have started using your helmet religiously, after the Chennai cops started fining
those who don't wear one while riding a bike. But do you strap the helmet securely ?

If not, you could as well not wear one because, in case of an accident, the helmet would
just slip off your head and not be the life-saver it should have been.

Thus, even when the intent was there, the purpose would not be served, due to not doing it
correctly. So, the next time you are out on the road, feeling the wind blow in your face, just
remember to strap up.

For, as the CCTP (Chennai City Traffic Police) says, you need hardware (helmet) to protect
your software (your brains).