Here is a picture. https://photos.app.goo.gl/RxiVCBeMDLR3Mze36
Also you can see the disassembled view here
https://oldgliders.com/en/offer/bfg-1600-electric-sailplane-epo-1600mm-pnf/
It looks like the two wings fit together and there are two rectangular holes which, when you line them up, you can jam a peg into?