system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are you always told to widen the crack before fixing it?

When you go to fix drywall or tarmac, the first instruction is to widen the crack. Why is that?
gpt
You widen the crack to remove loose materials and be sure to get the filler all the way in the crack. Nit widening could leave loose broken pieces that will inhibit the effective fix. Also, if the crack is narrow, it would be more difficult to get the filler all the way into the crack.