To improve readability and ease of use, you can hide parts of a structure. When you hide parts of a structure, they are normally displayed in grey (dimmed). Dimmed elements cannot be selected.
To make a part of a structure invisible, first select that part. Then click on the button 
to make the selected part invisible. If you want to do the opposite, i.e. make only the selected part visible and the rest invisible, click on the button 
.
To make the entire structure visible again, click on the icon 
.
If you want to switch between the visible and invisible parts, select the entire structure (only the visible parts are actually selected); then click on the buttons 
and in succession to make everything visible and then hide all selected bars (make them invisible).
