So I had a look at a small trench I dug yesterday and there's was a few inches of water and the sides were falling. Picture attached (I think can't tell on my phone). It might be worse as it's only 2m length but I'm thinking I need to shutter as I go. Unexpected as it's sandy not shrinkable grounds usually but had lot of rain all winter. Never done shuttering any tips. And is this the only way. Cheers.