I am about to lay these blocks and have a couple of questions. They are old blocks. I tapped off the old mortor with the back of a hammer. Do I need to do anything to the contact services to assure good adhesion before appling mortor? Also...I can't identify which side should be top/bottom. One side has broad flat surfaces while the other is much narrower. I suspect the broad surface should be up since it is easier to lay mortor on a wider surface. Please correct me if I'm wrong. Blocks are 4x8x16 double bullnose. Thanks, Bob
You are right - The surface with the wider face shells is the top. It is called a "mortar bed" because it allows a better bed of mortar without sloppimg excess mortar into the cores. - All block have a top and bottom. They are made in one way and turned 180 degrees to lay.
4" block can be fussy to lay because of the height to width ratio. As an example, and many good masonry contractors use a higher labor cost for laying 4" than 6" or 8".
Make sure you have removed all loose mortar and any mortar what could make leveling difficult. Use a Type N mortar, but Type S could also be used. For a small qualtity, definitely use pre-proportioned mortar in a bag.