While Deckard and Gaff are investigating Leon's apartment, Gaff creates a little stick figure out of some matchsticks and leaves it seated on a table. It's a symbol—and perhaps a clue to Deckard. The replicants themselves are like matchstick men (or matchstick women): they're made to be disposed, having a four-year time limit on their lives. Gaff might just create the figure out of restlessness, but in the movie, it seems overtly symbolic. Why else would you put it on screen?
In a way, it might be a hint to Deckard, as well. At the end of the movie, Gaff leaves behind a little origami unicorn—indicating (if you see the Final Cut or Director's Cut versions of the movie) that Gaff can read Deckard's dreams… because Deckard is a replicant. So when Gaff creates the little matchstick man, he might not just be commenting on Leon and the other rogue replicants… he might be giving Deckard a secret message about his own true identity.