Flood with cells?

Flood with cells?

I need to fill a cross section with cells. The purpose is to calculate the second moment of inertia, but that is not the issue right now.  When I use the pattern/flood tool the area is properly filled with the cells – but, they have lost their status as cells and I cannot change to other cells which was idea for the calculation process later on. (The replacement cells would have lines to represent moment arms)   Any other way to fill an area with cells?

Ingemar