*Got gutter nails that keep working loose.
Rubber cement. Fills the gap, glues them and remains flexible year round.
Got tree roots trying to enter your sewer: pour bleach in the bath drain a couple of times a month. Do it last thing in your day so it can set in the outgoing pipe overnight.
I have replaced those nails with screws in the past, but I'd be interested in trying the rubber cement trick.
I've used copper sulfate granules for roots.