Hi Morten, to build a Cheval de frise (german: Spanischer Reiter)
i will cling to what we have told the german players here:
viewtopic.php?p=34268#p34268There are no really existing rules for a Cheval de frise. With the exceptions, that you have to follow other safety rules to make sure that these things do not harm anybody else when falling into it.
Which bring us to a construction completely made out of foam. We recommend the use of:
Pipe Insulation Foam is cheap, and if you buy the thicker and more sturdier ones, they will stand up and not bend like a waterhose.
As alternative or just for the use as a cross beam in your Cheval de frise, most people use the socalled "Pool Noodles":
Just bind together with cord and paint it brown. Easy for transport, cheap and everywhere available.
If you want to build it following your own ideas - you have a complete freedom of design, but please:
-> It needs to be safe for everyone falling into it. Nothing that can break and come out and hurt people.