Background vs foreground

 
I have just started using Metatrade, and find it to be a very nice programme. My compliments to the designers.

Can I ask what effect does selecting "Draw object as background" have, in Line Properties, for example? I select this option, but can see no difference between this and leaving it in the foreground.

Many thanks.
 
try to insert some shape object or some channel or some thick line and see difference after switch background