This tip and diagrams are from the excellent British book “The Complete Guide to Climbing and Mountaineering” by Pete Hill.
A fixed line that takes a load can be tensioned over a sharp rock edge, resulting in possible damage to the rope, or worse.
Here are two possible ways to prevent it.
1) If there’s a gear placement next to the offending rock bulge, some well placed pro may offer a directional that can keep the rope off the rock. This gear needs to be very solid, as it may take the full load initially rather than the anchor.
2) If there’s no gear placement options, you might try this Crafty Rope Trick: Using butterfly knots, you can add a sling into the system that can abrade on the rock, possibly sparing your rope.
Finally, if you anticipate the rope being loaded over an edge, you may want to bring a designated rope protector length of hose like this one.