Preparation

• Protecting the bricks before applying mortar prevents the surface of the bricks from being acquiring a permanent gray stain. A simple way to do this is to line the edges of each brick with masking tape. This process takes time, but the extra effort will result in clean, crisp joint lines and stain-free bricks.
  
  

Mortar Application

• One traditional way to apply mortar between bricks entails smearing small amounts over each section and using a grout float to tamp it down. This method is quick, but it's also messy and more likely to leave stains than if you use a grout bag. Grout bags are open-tipped bags that require you to squeeze the grout along the joint, guiding the tip of the bag for a precise application.
  
  

Concave Joint Finish

• Mortar begins to harden quickly, so you need to finish the joints right after you apply the mortar. This involves smoothing the surface so that it’s free of bumps and pits. Running a concave jointer tool over the mortar will create a subtly recessed look that highlights the bricks. Jointer tools have a curved shape, with ends that align with the top of the brick to ensure uniform depth with each joint.
  
  

Flat Joint Finish

• If you want to finish the mortar joints so they’re level with the bricks, run the flat end of a trowel over the top to strike off any excess and fill in any holes. Hold the trowel so it sits flush over an adjacent row of bricks and move it slowly over each section. If you have a helper, one person should apply the mortar in small sections while the other follows behind finishing them. If you’re working alone, finish the joints in one section before applying mortar to the next.