A die-casting Zn—Al alloy fitting with four connectors is invented to simplify the assembly of a stainless steel BBQ grill trolley. Four connectors of the fitting connect two rectangular tubes vertically and two rectangular tubes horizontally. Eight fittings are required to assemble a BBQ grill trolley. Two channels are formed on two larger side surfaces of each connector with a compressible plastic plate inserted to eliminate the clearance between the fitting and connected rectangular stainless steel tubes.