This is more of a complete rebuild, rather than a true remix of the donnyb99 fantastic Y-Axis belt tensioner for the Creality CR-10 3D printer. I really liked the design, but felt that the tolerances were not where I felt they should be. The fit was way too loose and sloppy. I also experienced a failure whereby the head of the tensioning bolt pulled through the plastic wall. So I completely rebuilt it in Tinkercad using donnyb99's model as a template. I also added in extra stiffening/bracing, thickened up the structure quite a bit, made seats for the horizonal idler screw sleeves thus allowing more "bite" on the thread. It has a reversed knob for better grip remixed by Phillipe. The results are pretty awesome. This thing is very robust with way less slop and jiggle.
As noted by donnyb99, you will need one M5x25 bolt and a match nut (hex head is recommended for the screw).
Print the plate and idler slider with 100% infill. The Tensioner bracket should have at least 8 solid layers on the bottom with 40-50% infill. Print vertically with the 4 "legs" on the bed with minimal supports. Print at a slower speed to prevent detachment as it gets taller. Also use a nice wide brim of at least 8 loops.