Abstract: A high pressure mold assembly and method for holding a sheet of material such as glass while molding a gasket or other molded portion on the sheet from a thermoplastic or other moldable material such as PVC at high pressures of at least 2000 psi. The assembly and method provides an improved holding feature which reduces the percentage of broken sheets of material and yet controls the flash or overflow of the moldable material out of the mold cavity. The mold assembly includes a first mold section and a second mold section. The first mold section includes a first seal receiving surface which receives a first resilient seal while the second mold section has a second seal receiving surface which receives a second resilient seal. The seals engage and hold the sheet therebetween and accommodate variations in the sheet. Each of the seals is adapted to press and seal against the sheet for preventing the flow of the molten material along the sheet while under high pressure of between about 2,000 psi and 5,000 psi.