capture and retain inner longitudinal ribs 50 and 52 of the screen retaining gasket 20 the inner and outer longitudinal ribs 50 and 52 have a bulb style cross section 51 which is retained by the inwardly facing retaining flanges 48 a substantial depth of free space 46 see fig4 exists inwardly of the lowermost of the serrations 40 and a bottom surface 54 of the channel 18 the depth of the free space 46 allows for a broad range of adjustability with respect to tensioning the screen 16 the framing members 14 may be made from a variety of metallic and plastic materials one exemplary preferred material is extruded aluminum referring to fig4 the screen retention gasket 20 features the spaced apart longitudinally miming upper 50 and lower 52 ribs with a bulb style cross section 51 on an inner face 56 of the gasket 20 for engagement with the spaced apart inner 42 and outer 44 lower interior longitudinal channels formed in the lower interior wall 38 of the cross section 18 of the framing members 14 on an opposite outer face 58 of the gasket 20 are serrations 60 for engaging the mesh of the screen 16 the screen 16 is inserted into the channel section 18 such that the u shaped hem 30 of the screen faces away from the serrations 60 in the retaining.