I could not find anything on here for this issue, which only means my skills at searching for it are very poor. Anyway, these clips simply just keep separate board game boards together and aligned. I made sizes for 2, 2.5, 3, 3.5, and 4 mm thick boards. One of these sizes should fit your needs. The bottom is the tang with the inside chamfered lip.

No

Normal

90%

Print standing on end for strength.