X Belt holder self locking

5th April Update: the block was 10 times too big. I scaled it down and uploaded as v3.

After I printed a new X-carriage https://www.thingiverse.com/thing:2469435 for my Anet A8 I realized that the included X-belt holder by itesdahl was to big for my GT2 belt. When tensioning the belt it always slipped a tooth.

I found the X-belt holder from c0ryp1 https://www.thingiverse.com/thing:2795893 but that holder didn't have the right holes for the X-carriage.
I used his locks but designed quickly