Refixing the rope is a common practice to avoid rope damage while top rope soloing.
After rappelling down from a primary anchor, especially if going over a sharp edge, you take a moment to re-tie the rope at the next protection point. That lower point takes the weight of the climber, but is backed-up by the above anchor, without weighting the edge each fall/take.
But, what knot to use?
I recommend the alpine butterfly for re-fixing the rope. Clove hitches are perhaps most popular, but have a serious drawback.
A clove hitch cinches tight against the carabiner, stays in one position, and thus wears the rope very aggressively against the rock at a single point. The bit of movement of the alpine butterfly loop spreads out the wear and is easier on the rope if you expect multiple falls.
This refixing is generally for the top of a pitch, where I don’t mind stopping and weighting the rope to untie the knot with two hands. For mid-pitch refixing, I use a slip knot, or just strategic rope protector use.
