A hand truck is provided with upper and lower frames; two hinges connecting the upper and lower frames; wheel assemblies connected to the lower frame; and a load support assembly connected to both the lower frame and the wheel assemblies to have an operative position extending forwardly of the lower frame. Each of the upper and lower frames includes two side rails each having two parallel frame members and a guide groove defined by the frame members. There are further provided an arcuate bar interconnected the hinges; and a lock assembly between the guide grooves of the side rails, the lock assembly including two opposite sliding members. The sliding member includes an insert section in the guide groove and having a first wing, a second wing opposite to the first wing, an extension extending out of the second wing, and a cavity.