Zee Strip is a notched retrofit sub-purlin that seats over the existing roof ribs, so a new metal roof can go on over the old one without tear-off. The lower-cost choice when the reroof adds no new load. Profiles for R-Panel, 2" vertical-leg standing seam and trapezoidal rib, in heights up to 6" for added insulation. 50 ksi G90 galvanized steel; patented anti-rotation arm optional. Made in the USA. Details: https://www.tophatframing.com/zee-strip-for-metal-reroofing.html