So, basically, you want to screw the mounting base of the Reelcraft reel to the side of a rafter? As in an attic? So I assume you have exposed rafters and no ceiling joists?
(Rafters are those angled boards that your roof sheathing is attached to.)
And you want the hose spool to be laying ,more or less on its side, at whatever angle your rafters are at, so that it spins semi-horizontally, rather than vertically?
Or do you mean a joist, and it will sit exactly horizontally, screwed to the side of a joist?
You know, a picture of this location where you wish to mount the hose reel would be helpful, because this is hard to envision.
I think the manufacturers specs for pretty much all spring return hose reels will say that the spool must be vertical for proper operation.