Staff at a bookmakers in Greater Manchester barricaded themselves in the toilets when masked raiders tried to smash their way to the tills.
Two men, armed with baseball bats, burst into Coral in Chapel Street, Audenshaw, Tameside, at about 2010 on Monday, police said.
They shouted "give us the money" at the cashiers and started smashing the protective glass around the staff area.
The cashiers ran to the toilets and the robbers stole cash and fled.
The first robber is described as a white, in his late 20s and of stocky build. He was wearing a black hat and a dark winter jacket.
The second is also described as white and in his late 20s. He was wearing a high visibility jacket and a navy balaclava.
Det Con Richard Sewart said: "This was terrifying for the staff who fled for the toilets the moment they saw the violence these men were prepared to use to break into their staff area."
He appealed to anyone with information to contact police.