Concrete edger produce a neat rounded edge along the slab perimeter which helps the slab resist chipping and spalling damage after the forms are removed. An edger looks like a small trowel with one curved side.
WHEN & HOW TO EDGE CONCRETE
Perform edging after the bleedwater disappears from the concrete surface, but before the forms are removed. The concrete should be firm, but still workable. Edging can be done along with jointing.