Translations:Adventist Youth Honors Answer Book/Vocational/Masonry/9/en
From Pathfinder Wiki
The S-tool should be used sometime between the time that the mortar is placed, and when it begins to harden. If the S-tool is used too late, then it will result in uneven lines throughout the mortar. The mortar will not have a smooth concave surface, and will look very raggedy.
