Useful sandpit

we bought the sandbox this spring. The structure is not so simple, since no holes are pre-drilled and the boards do not abut each other. The boards are stable, but were also doing what with larger knots. We have every board penciled and drilled individually. Is certainly easier but we were least sure that it fits. Be careful when drilling, the boards are made in different thicknesses for side panels (20mm) and seat parts (30mm). The links are unfortunately only of plastic, which does not make too much stable the entire structure. 'M curious look like this after 2 years. Built the part has a diameter of 145cm.
In order not to turn the sandbox in a litter box and the matching tarpaulin was sold out, I have a tissue-Plane hobby with 2x2 m and bought 4 meters Expander rope works. To play sensibly in the box, we have about 200 kg play sand needed.