You can use the Create center elements between parallel lines function in the Tools menu to create elements and their associated parts between parallel lines. The element thickness is automatically taken from the vertical distance between the two lines.
Select the lines with the mouse one by one in the work window. As soon as you move the pointer over the second line, you can see the element in a preview.
Material
In the list of already created materials, you can select a material, edit it, or define a new one.