Sorry to disagree, but pulshakha is mistaken, at least as far as SAP version 8 is concerned. You can draw a line in space anywhere you want, NOT just on gridlines. You can do this by a) Draw joints anywhere you want, then right click the joints to modify X,Y,Z coordinates or b) draw a line approximately where you want it, then select joint and Edit move, or use reshape to move the line where you want. It does not have to be drawn between grid intersections.
Also, you may note that the Draw joint gives you the option to specify an offset dimension which draws the joint offset from wherever you click, a feature I often find useful
SAP2000 is not Autocad, but many of the functions are very similar to Autocad