Under Clause 7 "Additional design and construction considerations", point 7.1 "Climbing", DIN EN 953 states that climbing on guards shall as far as practicable be inhibited by design.
Climbing can be made more difficult, for example, by eliminating horizontal structures and the horizontal component of mesh fabric from the outside surface of the guard.
The standard does not state precise dimensions and specifications. That is at the discretion of the design engineer.