This is Leveling Brackets for Tile Leveling System that you can use between different tile planes on the wall, so you can have the same line. Leveling brackets simplify tile installation at 90° corners.

Fixes two tiles in a 90° plane. Installation tips: 

1. Apply the tiling compound (Mortar, Adhesive, Thinset, etc.) and lay first tiles on the corner. 

2. Install the clips 1.2 inches from the edge on each side of the corner. 

3. Install the leveling bracket on both clips. 

4. Insert the wedges into the clips with leveling brackets and tighten it with pliers or by hand until the tile is leveled. 

5. After the floor compound has completely cured (approx. 24 hours), remove the system by hitting it along the joint with a rubber mallet.