How does CAD work from a floor plan, to an elevation?

First define your floor plan as a block,

then enter the command: xc

Select Objects: 1 found

Select Objects:

Enter Clipping Options

[On(ON)/Off(OFF)/Cut Depth(C)/Delete(D)/Generate Polyline(P)/New Boundary(N)] : n External Mode - Objects outside the boundary will be hidden.

Specify the clipping boundary or select the reverse option:

[Select polyline(S)/Polygon(P)/Rectangle(R)/Reverse clipping(I)] : r

Specify the first corner: Specify the diagonal:

Follow the prompts and do it step by step It's very easy to use, and if you want to take a part of the figure you can take a part of the figure to draw the elevation is very convenient. I hope to help you.