Wooden Super frames with 7/8` top bar, Hoffman self spacing side bars with grooves and 2 pieces for the bottom bars.
S.N.4 frames are used in a National or WBC super. S.N.4 frames have hoffman spacing side bars.
Top bar- 17″ x 7/8” (431mm x 22mm)
Side bar- 51/2” x 1 3/8” tapering to 7/8” at bottom (140mm x 35mm)
Bottom bar- 14″ (356mm)