So the banister holders are in plaster, and it's pretty crumbly. We removed the wooden rail, but the anchors are in no way attached to the wall soundly. How can I make this secure again?
Home Improvement Stack Exchange is a question and answer site for contractors and serious DIYers. It only takes a minute to sign up.Sign up to join this community
Move the anchors to a stud and attach them with long screws. Use a stud finder (preferably with a deep scan capability since you mentioned plaster) to locate your studs. Or you can drill some small test holes since you already need to patch the wall.
Don't use drywall screws, you need something with more shear strength. I wouldn't use anything less than a 2" screw, particularly in the top two holes. You need it to have a good bite into the stud.
Then you just have to patch and paint the old location.