The unpleasant realization that, when assembling a purchased product, the painful discovery that the manufacturer has not included enough screws, bolts, nuts, etc. to complete the assembly. The word is derived from the character of Scrooge depicted in Charles Dicken's "A Christmas Carol". The word represents the frustration created by a manufacturer's miserly policy of not spending just a few extra cents to make sure enough parts were provided for proper assembly
Jack was assembling the bicycle he had bought for Johnny, but found out he was screwged when there weren't enough bolts supplied.
A towel, or other absorbent material, used to protect a bed, bench, chair, etc., from the residue moisture left over on one's posterior after a shower, bath, or swim. The towel acts much like a coaster that is used to protect furniture, except this time it's protecting the bed from your wet butt.
"Can't you please use a butt coaster" said Jean, after I got our bed wet by sitting directly on it after coming out of the shower.