Today I remembered when I was in high school I got some hand soap for my (personal) bathroom (in my room that nobody ever used) that I really liked (it had beads) and wanted to make last a long time. So I taped a note on it that said "Only pump this soap on your hands once and no more. Thank you." Then I thought it was funny to sign it "- Staff"

so 

dumb

but it worked! nobody pumped my soap on their hands

(because nobody used that bathroom except me)