I have hired a few skips in my day and never had a problem with anyone "using" them. As Marmora Man says, you are just as likely to have someone grab something and take it away If had a specific project on and needed every cubed centimetre of space then I would take steps to discourage people - but to say it;'s no better than fly tipping is a bit inaccurate. Fly tipping = ugly mattress/washing machine on side of road, uninvited spoiling the vibe People putting stuff in your skip = an already-in-place unattractive unit, probably not full and probably not going to be, which is being used for the temporary storage of unwanted rubbish. Who fills it is not really the point. Yes, the owner is paying for it but what's the harm overall? (with the exception of aforementioned planned projects which NEED every bit of space - in which case, take steps to inform people)