An old expression dating back at least to British National Service (1950's) and probably a lot earlier. Possibly for as long as there have been British Armies that supplied blankets.
Was also commonly used in former British Territories and Dominions (Australia etc.) which now form the Commonwealth.
To attach to something very securely.
Also to hang around something or someone very persistently.
"This glue will stick that on the wall like shit to an Army blanket."
"He's stuck to his boss like shit to an Army blanket."
The snake in the blanket is more or less the male version of camel toe. It is when a man's pants are so tight you can clearly make out the outline of his penis and nutsack combo.
A snake in the blanket is very sketchy and can create many awkward situations. Use extreme caution when in the presence of a snake in the blanket, or you may die.
An amazing fort made out of sheets, clothes pins and clips inside which you can do a lot of fun things. Like, sleep, colour, cuddle.....Or just sleep. For all ages, irrespective of what people say.
Me : I'm going to build a blanket fort.
Mom : You're too old.
Me : ......*builds blanket fort*