An open wrench includes two heads overlapped to each other, two covers connected to top and bottom of the heads, and a pawl. Each head has a first recess, a recessed section, a contact face, and a second recess. The pawl is movably located within the second recess. The pawl has a first engaging portion, a second engaging portion, a reception slot and a curved slot. A resilient member is located in the reception slot. A pin extends through the covers and the curved slot. The pin contacts one end of the resilient member and contacts one inner end of the curved slot. When an object is located in the first recess, the contact face contacts one side of the object, and the first and second engaging portions contact two adjacent sides of the object. The object can be rotated continuously.