This is the male part of the Thule hinge support leg joint. The female part can be ordered separately,
for example at: https://www.vorselaarsrecreatie.nl (Thule Female Hinge Support Leg V2-
1500601603),
but the male part is only for sale complete with the support leg.
The best is a print in metal (on demand printing company) which is stronger than a PETG printed
part as shown here.
Printing with print plate support only and 0.4mm nozzle.
The author marked this model as their own original creation.