from the shingles with blocks 42 lag bolts 43 are used to secure the stringer directly to the roof as shown these bolts should be coated with a sealant when installed to prevent leaks usually three spaced horizontal stringers are used to mount the collector units 10 composite of frame 20 and absorber 13 and are arranged so that the guides 30 rest on the top of the stringers see fig7 opposed c brackets 44 are used to attach the collector units to the stringers the width of the c brackets is such that it will span the guides 30 of two adjacent collector units with room for a screw 45 to pass therebetween when the screw 45 is inserted into the stringer the adjacent collector units are properly secured in a manner by which they are suspended above the roof this avoids the heat loss from conduction to the roof that occurs where the absorber lies directly on the shingles if there is no adjacent collector unit an l shaped bracket 46 provides a spacer for the c brackets as shown in fig7 fig8 shows how the collector units 10 can be nested together on the mounting stringers 41 however before the adjacent units are secured to the stringers a floating nipple 50 is inserted into the open ends 12a of the manifolds or headers 12 the nipple has a rubber cuff 51 centrally received on its hollow cylindrical core 52 proximate to each end of the core a groove is formed and an o ring 53 is inserted this nipple is limited in its axial movement in the open end 12a of each header by an interior step.