• Scratching the mortar
• An inexpensive notched tile trowel works well to prepare the mortar for solid bonding.
• Grooving or scratching the wet mortar provides a better bond for sticking on the stones. You can buy a special rake-like tool for this, but we prefer to use a 3/16-in. square-notched tile mastic trowel. They’re cheap and easy to find at home centers and hardware stores. Simply drag it across the wet mortar to make horizontal stripes.
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