New garden - edging

Hello all,

Just moved house and the back garden is just soil and (a lot of) rocks. I've never had a garden before so it's all new to me, but I'm enjoying it so far. I've got a reasonable idea about what I want to create in the garden, but I'm not sure if it'll turn out how I vision it to be!

I need to partition off a bit of the garden so I can get it dug up, remove the rock and sow some grass seeds. This is really the first stage; loads more after like decking, trees, plants, raised veg beds, etc.

I'd like a sort of rustic style to the garden so thought of using tree trunks as edging, dividers if you like between the grass and other areas. I'm not sure if it's exactly tree trunks I'm after or perhaps that logs they sometimes use in kids play parks, does anyone know what I'm talking about? I can't find either to buy and I'm not sure where to look. I can't just go and cut down some trees. Anyone know what I should be asking for or looking for here?

Thanks,

Gary.