A method and apparatus for making thin panels having a urethane core and hinges for interconnecting them. A frame is secured to a support bed, and a sheet of paper is placed inside the frame into overlying relation to the bed. Plural board members are then placed inside the frame so that they overlie the peripheral borders of the sheet of paper and so that they are held in position by the frame. Tubular members are positioned in bores formed in the board members so that they extend into the area bounded by the extrusion members, and the innermost end of the tubular members are taped over to prevent foam intrusion. A second sheet of paper is then placed over the frame and a rigid top plate is lowered into overlying relation to the second sheet of paper so that the frame is sandwiched between the bed and the top plate. Foam is then injected into the cavity defined by the board members and the sheets of paper through a port formed in a board member. After the foam has cured, the top plate is raised and the completed panel is removed from the bed. A tool is used to form a bore at the innermost ends of each tubular member to accommodate a retainer clip that engages the innermost end of its associated tubular member, and a bungee cord is extended between opposing retainer clips in adjacent panels to form a double-acting hinge between the panels.