DIY Betterly straight line connector?

[kwakefield]

Has anyone tried to diy their own version of the Betterly straight line connector for joining guide rails?
It looks fairly straight forward except I’m getting stumped on how the two clamping bits work (mechanically).
Yes, I know using a long straight edge or level will work, but I’m looking for a solution somewhere between that and the Betterly.

Thanks