Class V Cavity Preparation
To prevent displacement, incisal (occlusal) and gingival grooves are placed along the axial wall in an incisal (occlusal) and gingival direction.  Note the minimum resistance form requirement of 0.75 mm with no less than 0.5 mm within DEJ.
A 1/4 round bur is used to prepare these 0.25mm-deep grooves at the inciso-(occluso-)axial and gingivoaxial line angles.
RETENTION FORM
Class V, Page 3
Occlusal and gingival walls alone do not provide retention form
Retention grooves do not go into axial wall