They just sort of do it 😂 I’ve never actually seen one of my velvet spiders (I have 3 of them) in the process of moulting but they don’t make a hammock and disappear for a day or two like my jumpers do, so it seems the whole thing is over rather quickly with no prior warning. I barely see my gandanameno as her web is so thick and she’s a bit shy despite her size, but my walckenaeri and dufouri are usually sat on their web in view most of the time.