Beat the drum

If you beat the drum you promote, publicize, or advertise a product or service. 

“The coming year we'll have to beat the drum for our new product.”

Batten down the hatches

To batten down the hatches is to prepare for an imminent danger or emergency. 

“Storm is brewing, so batten down the hatches!”

Bark up the wrong tree

To bark up the wrong tree is to mistakenly blame someone for a wrong or error committed by someone else. 

“The police arrested the victim instead of the offender.  They’re barking up the wrong tree in their investigation.”

Baker's dozen

A group of 13; from the old custom among bakers of adding an extra roll as a safeguard against the possibility of 12 weighing light.  

“A baker’s dozen is a dozen plus one.”

Bag of bones

Someone is a bag of bones if he is severely underweight.  

“He was a bag of bones when he returned from his tour of duty.”

Bad workers always blame their tools

  

People who perform badly always have something or someone to blame for their poor performance.  

“He doesn’t want to admit that he failed the exam because he did not study.  He says the time was too short, the room was crowded, etc.. Of course, bad workers always blame their tools.”