Photograph your parents' bathroom. Get the bars drawn exactly where they go.

i have this conversation with families about twice a week and it always stalls at the same place — everyone agrees something should go in, nobody can picture where. so take one photo from the doorway and it draws them in: bar by the toilet, bar along the tub, stool, night light, and the mat gone because the mat is usually the actual problem. then you can just show your dad the picture.