A sign one could see all along the site. I was intrigued by the image in the right hand bottom corner, after some thinking I came to the conclusion that it means: do not raise a load from your back, but from your knees. Good advice. I confess to having ignored the “do not enter without permission” part, as getting permission required entering. The other signs are concerned with “Safety first”, “danger of falling” and “danger of slipping”, of getting too close to machines and wearing all sorts of protective dress.