A shop worker fought off two masked raiders in Bolton using one of his shoes to defend himself.
Police praised the man's "heroic actions" as the robbers left empty-handed from a service station in Westhoughton.
The member of staff took off one his shoes and grabbed a glass jar when he was confronted by the two robbers at 1.20am on Saturday.
One of the raiders wielded a knife as the shop worker successfully fought them off, police said.
The victim suffered two puncture wounds to his arm and needed 12 stitches.
Both suspects were black, with one described as 6ft tall, of medium build and in his early to mid 20s. The other was around 5ft 9ins and of medium build.
Police are appealing for information to trace a woman who walked into the Mercury Service Station seconds before the incident.
Detective Constable Malcolm Cheetham said: "This man's heroic actions meant that these thieves were able to get away empty handed, but for his trouble he was wounded.
"We will do all we can to find the men responsible.
"We are appealing for witnesses, but in particular we need to hear from the woman who walked in only moments before but didn't stick around to give the police her account - probably because she was so shaken up."
