define the upper channel 40 for receiving a lower edge portion of glass panel 100 the lower mounting portion 46 of female rail section 20 defines a vertical depending leg 60 and a horizontal wall 62 the inner surface of leg 60 defining a lower clamping surface 61 that cooperates with surfaces 36 and 37 of the male rail section 18 to define channel 42 in the embodiment of the invention illustrated in the drawings the clamping assembly 22 comprises a plurality of equidistantly spaced threadably engaged bolts 64 and nuts 66 that project through a corresponding plurality of aligned apertures 66 u2032 and 66 u2033 in the central walls 28 and 48 of rail sections 18 and 20 as seen in fig3 tightening of the nuts 66 about bolts 44 preferably with a torque wrench to ensure uniform tightening pulls the two rail sections together causing the upper clamping surfaces 33 and 56 to bear against the sides of a gasket 70 and glass panel 100 and the lower clamping surfaces 37 and 61 to bear against the mounting surface to effect the securement of the rail 16 to the glass panel and mounting structure a u shaped gasket 70 formed of a suitable flexible rubber or plastic material preferably is provided in channel 40 between clamping surfaces 33 and 56 to enable the rail sections to securely grip the glass panel without scratching or otherwise damaging the panel as seen in fig2 with the rail sections joined together by the clamping assembly 22 the extended end 38 u2032 of the wall 38 on the male rail section 18 abuts the upper end of the clamping surface.