The Last Resort font is a collection of glyphs to represent types of Unicode characters. This provides users with the ability to tell what sort of character it is, and gives them a clue as to what type of font they would need to display the characters correctly. Overall, there are a number of advantages to using a Last Resort font for unrepresentable characters. Operating systems are freed from the overhead of providing a full Unicode font.
Users see something more meaningful than a black box for unrepresentable characters.
Users familiar with the scripts being represented with the Last Resort font will readily identify what needs to be installed to represent the text. Users unfamiliar with the missing scripts are shown easily-identified symbols rather than lengthy strings of unidentifiable characters. Unicode blocks are assigned a glyph for a representative character typically from that block. That glyph is chosen to be as distinct from glyphs from other blocks as possible, to reduce confusion. In addition, all of the missing glyphs are in a rounded rectangle, to provide a common, recognizable element.