By John Flanagan
Introduction
Use the Split Element Tool to cut an element (such as a wall or line) at a selected point. The Split Element Tool is located on the Modify Panel.
Fig 1: Split Element Tool Location
To guarantee that you split a wall exactly on a grid line, just split the wall to the left or right of the gridline and then change the temporary dimension between the split and the gridline to zero. The split will now move to be exactly over the gridline. Refer to the following illustration for guidance.
Fig 2: Split Line Location
Check the results in 3D. You will see that the wall has been split straight through at the specified gridline.
You would use this technique if you wanted to change part of the wall to a different wall type.
Fig 3: Wall Types (the wall on the right of gridline 3 has been changed to a curtain wall type) 