Groover (jointer)
A hand tool that presses a groove into fresh concrete to form a control joint, creating a weakened plane where shrinkage cracking is directed.
What does groover (jointer) mean?
A tooled groove only works if it is deep enough relative to the slab thickness; a shallow decorative line does not control anything. Hand tooling is limited to fresh concrete, so on larger slabs sawing replaces it. Grooving also leaves a rounded, finished-looking joint that many homeowners prefer visually to a saw cut.
In practice
The joints in a residential sidewalk are usually tooled with a groover while the concrete is still plastic, not sawed later.