A method for making a mushroom-type hook strap for mechanical fasteners, the method comprising the steps of: providing a rotational molding roller, the molding roller having a plurality of substantially Y-shaped molding cavities formed in an outer periphery surface thereof and a cooling device provided therein; providing an extruder, the extruder having a extruding die disposed imminently close to the outer periphery surface of the rotational molding roller with a gap being formed therebetween; feeding a thermoplastic material to the extruder and melting the thermoplastic material in the extruder so as to extrude the melted thermoplastic material into the plurality of substantially Y-shaped molding cavities and onto the outer periphery surface of the rotational molding roller through the extruding die; cooling the thermoplastic material on the outer periphery surface of the rotational molding roller and within the substantially Y-shaped molding cavities with the cooling device so as to form a hook strap on which an plurality of hook prefroms are molded, each preform having a substantially V-shaped free end; peeling off the hook strap from the molding roller; and feeding the hook strap through a nip formed between a pair of calendar rolls, wherein the calendar roll that contacts the V-shaped free end of the hook preforms is heated to a temperature above a plastic deforming temperature of the plastic material so as to deform the V-shaped free end of each hook preform into a polygonal head shape and thereby forming a mushroom type hook having a polygonal head portion, the polygonal head portion providing protruding portions in substantially every direction for engaging fabric loops of a loop strap. providing a rotational molding roller, the molding roller having a plurality of substantially Y-shaped molding cavities formed in an outer periphery surface thereof and a cooling device provided therein; providing an extruder, the extruder having a extruding die disposed imminently close to the outer periphery surface of the rotational molding roller with a gap being formed therebetween; feeding a thermoplastic material to the extruder and melting the thermoplastic material in the extruder so as to extrude the melted thermoplastic material into the plurality of substantially Y-shaped molding cavities and onto the outer periphery surface of the rotational molding roller through the extruding die; cooling the thermoplastic material on the outer periphery surface of the rotational molding roller and within the substantially Y-shaped molding cavities with the cooling device so as to form a hook strap on which an plurality of hook prefroms are molded, each preform having a substantially V-shaped free end; peeling off the hook strap from the molding roller; and feeding the hook strap through a nip formed between a pair of calendar rolls, wherein the calendar roll that contacts the V-shaped free end of the hook preforms is heated to a temperature above a plastic deforming temperature of the plastic material so as to deform the V-shaped free end of each hook preform into a polygonal head shape and thereby forming a mushroom type hook having a polygonal head portion, the polygonal head portion providing protruding portions in substantially every direction for engaging fabric loops of a loop strap.