Surveillance video shows two men walking into the business on Shaw and Marks Avenues on Sunday.
One of the men tried to take off with hundreds of dollars worth of items, but an employee stopped him before he could leave.
The man then pulled out a knife and threatened the worker.
The employee could get back some of the power tools before the two suspects ran off with the rest of the merchandise.
Anyone with information on the men is asked to call the Fresno Police Department or Valley Crime Stoppers.