Wasn't quite sure what to call this one, but hopefully this does justice.
We've all had it happen. "Damnit, there's totally enough room here why can't I get it to place!"
I noticed that if you cannot place cover, your soldier will move a little bit and try and find a way that it can be placed. This is a wonderful feature and is super helpful at times, though another idea I had was simple. What if there was a green highlighted area where the sandbag you're placing would be? It would allow people to better place their sandbags in much more neat and effective fashions.

Above is my proposition for a fix. Essentially, render the area the sandbag will be placed with some form of visual cue that shows the exact placement of the sandbag. Perhaps it could be red if it can't be placed in that location. This would allow people to tightly knit their sandbags together and plan more effective foxholes and the like.
I apologize for the poor quality of the image, it was a rushed product in photoshop that I threw together in a few minutes to illustrate my idea.
Any feedback is appreciated, and I look forward to seeing you all on the frontlines.