Black lines between objects

I’m gettin an strange problem wneh creatin the game level.
If I put 2 level wall pieces together, there is a black line between them.
I’ve changed the texture, the size… but the black lines are always there.
Any way to fix it?

Is the line still there even when the mesh has a plain white material? If so it might just be that the meshes aren’t aligned exactly. If so either you need to move the gameObject slightly, or you need to edit the actual mesh outside of unity. If not, try changing the import settings on the image file used as your current texture. Try changing “Clamp” to “Repeating”.