I get up on my roof about once a week with an electric leaf blower to blow off the leaves. I notice that, sometimes, the cord gets caught under a corner of a shingle. The other week, I noticed that one shingle had a corner missing.
Do I need to replace this shingle? I don't want a leak in the house.
Should I use roofing cement or something to glue down all the shingle corners? It's a big area.
Just be careful with the cord from now on. If you can find the broken off corner, just apply 2-3 small quarter sized dabs of roofing cement from a caulk tube under the broken tab to put it back into position.
It probably will not leak, even if you do not do that, but better safe than sorry.