To preserve it. I have my dad's funeral flag in a shadow box. I would never display it because I want to have it saved for future generations. The sun will zap a flag in no time. Also, in a shadow box it is still in the forum it was presented to the family; a triangle. What exactly do you mean by displayed properly? Just wondering.
Flag code states: The flag should never be used as wearing apparel, bedding, or drapery. It should never be festooned, drawn back, nor up, in folds, but always allowed to fall free. Bunting of blue, white, and red, always arranged with the blue above, the white in the middle, and the red below, should be used for covering a speaker’s desk, draping the front of the platform, and for decoration in general.