How can I set the height of the block to be the same as the parent's?

Question

css

Dear experts! Here's the problem, the side menu rides relative to its parent div class="menu_rail", but it doesn't have a fixed height, since its height must be set by section class="middle", but it doesn't because section class=" itself middle" is given by section class="content" and its content. Attention, question! How to set the height of the div class="menu_rail" block, which will directly depend on the height of the neighboring block. The design is responsive.
section class="middle"
div class="menu_rail"
section class="content"
div Content /div
div Content /div
div Content /div
/ section
/section

Answer 1

Maybe I did not understand, but in your question the inheritance of the parameter of the parent block was asked. This is set by the inherit value.