Using this option you can turn off/on the "wipeout" functionality (make opaque signs).

It can be a problem to get the signs clearly displayed on a sign plan where the plan/map basis is very detailed. Wipeout is an invisible object that goes behind the sign in "Outline" mode. This object will automatically remove all lines below the sign, see example below.

Without "Wipeout -

With "Wipeout" -

Note: This menu option has no effect on the signs as long as they are displayed in "filled" mode. All signs in "filled" mode will automatically remove background information.