Sometimes, when you are working with fillings to determinate the area of a building you select the slabs inestead of the filling, which is very annoying. Is there a chance to disable the selection of slabs.
Also pay attention to what pre-highlights before you select it and read what is says in the little pop-up info box.
As Stephen said, by activating a tool first you will have preference to select that type of element first (must use SHIFT key of course to select).
When you have overlapping elements watch the info box and use the TAB key to cycle through all the available possible selections.
One of the forum moderators. Versions 6.5 to 25 Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10 Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10
Or you could turn off the slab layers while measuring. I almost always have the ceilings turned off and sometimes the roof for that reason. I find it easy enough to toggle through them, and if need be, you could always set a Layer Combination.