Marrows & Squash - what to place underneath the fruits?

I've done both with or without something and not noticed anything different.  The only time I had problems were during the awful early summer of 2012 but it was mainly slug and snail damage

Summer squash I don't use anything- they are not there long enough.  Pumpkin family (butternut, spaghetti, pumpkin) I slip a little bit of thick cardboard underneath if they are on the soil.  If they are on a dry path material I don't use anything.