You could pound some wood stakes into the ground next to the timbers and screw them into the sides. Ideally use pressure treated if you want it to last. I am not sure if they sell pressure treated stakes, but you could make your own if you have a table saw.
RightYouAreKen1 t1_j9rc7or wrote
Reply to I’m building a border around a playground with landscape timbers, and wanting to secure it with something other than rebar. by _aPOSTERIORI
You could pound some wood stakes into the ground next to the timbers and screw them into the sides. Ideally use pressure treated if you want it to last. I am not sure if they sell pressure treated stakes, but you could make your own if you have a table saw.