As far as how/where to hunt it....I don't think of rub lines as "rub lines" but as buck travel corridors. What defines afternoon vs morning sit is the same as any travel corridor, relation to bedding, feed, and does. Hunt it like you would any travel pattern and let all the same things such as wind, access, cover, topography, proximity to doe travel/bedding/feed etc dictate how to hunt it.
Don't fall into the "which way was he headed" trap...Which side of the trees the rubs are on doesn't mean much..... Actually most of the signpost or territorial rubs I've actually observed being made or hit, with my own eyes, were made at 90 degrees to travel route....what I mean is, buck travelling a north/south trail headed north. Tree on right side of trail, rub ends up being made on southwest or West facing side of tree, if you see what I mean. Have a buck hit it from the other direction, now you have a rub basically facing west.
When looking at territorial or travel route rubs or rublines I am as much or more interested in historical older rubs than this year's rubs. This year's deer may be dead already. Historical rubs along with new rubs on the same line mean this travel pattern is used by successive generations of bucks for one reason or another....and likely will be used again in the future.
Now the next level is figuring out what the "for one reason or another" is.
R