What if the roof is blocked?

If it is a building, discuss it with the owner downstairs. There will be an openable inspection slipknot in the same position on his roof. After opening, clean up the sundries. If not, your building is well built.

Single-storey house

If it is a bungalow, or there is no slipknot, find an impact drill, remove the drill bit, install a steel bar with a diameter of 6MM (half of the drill bit connected with the impact drill should be welded to the steel bar head), and gently dredge it down.

Mastery of attention

Grasp the precautions in operation. I found this method in my work. I used to work in the property engineering department, specializing in decoration. This kind of thing often happens. There is no good way. Maintenance workers can only find these two methods. Cement is getting harder and harder when it is wet. Just try it.