Necessity is the mother of invention
 

Had problems with the boot on the rear wheel cylinder, it had perished around the big end where it sits in the groove on the cylinder, what to do.

Getting a new one is weeks away and it really needs to be sealed now.

A big piece of heat shrink would be good but alas none in the cupboard.

Think, ok, PET bottles shrink and shrivel up in a fire, Mmmm.

Cut the neck end off the 600ml bottle to suit end profile of boot, slip over and heat with an electric heat gun.

Wow, it works, I'm waiting on new brake reservoirs so the old ones still on the truck got the same treatment as they were perished and leaking. Cleaned up around them and I'll see if it leaks overnight.

DEFINITELY NOT FOR ON ROAD USE.

A good stop gap it would seem.