Today's Idioms are brought to you by the letter B! I went with three because I couldn't choose, but shortened the explanations.
1. Sheila had to choose between admitting she didn't practice, or trying to fake her way through it. She was Between the devil and the deep blue sea.
Meaning: Between two great dangers and not knowing what to do.
Origin: In the early 17th century the heavy plank fastened to the side of a vessel as a support for guns was called the devil. Sometimes a sailor had to go out onto this plank to do repairs to the boat. In heavy seas he would be in great danger of falling overboard and drowning because he was "between the devil and the deep blue sea."
2. Karl spent his vacation installing wooden floors, then went back to his construction job at the end of the week.What a Busman's holiday!
Meaning: spending your free time doing the same thing you do during working hours.
Origin: In London, during the late 1800s and early 1900s, buses were pulled by horses. Some bus drivers loved their horses so much that on their days off from work, they would ride on their own buses just to make sure that other bus drivers took good care of their horses.
3. Don't Buy a pig in a poke!
Meaning: to buy something without seeing or examining it.
Origin: A long time ago in England, a small bag or sack was called a poke. Farmers carried their pigs in pokes to sell at the market. Sometimes customers were cheated, as dishonest farmers would put the runt or even a cat in the bag. They would say they couldn't open the sack to show the customer because the pig would run away. So if you bought a "pig in a poke" you paid for it without examining it. This is related to the expression: Let the cat out of the bag.