[dakareng]

On the other hand, there may be an official guard that is not specific to a chapter. Pi Beta Phi's official guard is our crest.

A guard is not necessarily simply to 'protect' the badge (and some badges are better suited to bubble guards than others-- our badge is thin enough that most bubble guards and earring backs add weight that makes the angle wrong). Depending on the badge, a guard can add more 'bling' to it that just makes it look nicer, no matter how functional it is. Personally, I like our crest guard... Tri Delta's trident guard is another one that adds to the beauty of the badge.