Instructions
Click the "Build Mode" icon.
Click the "Wall Tool" icon.
Move your mouse over an open square on the map. The "Wall Tool" will automatically snap to the edge of the square.
Hold down the left mouse button and drag the "Wall Tool" across the lot. The wall will automatically form as you drag the "Wall Tool." Drag your mouse as far as you wish for the wall to extend.
Release the left mouse button and stop dragging your mouse once the wall is as long as you want it.