Matricing involves creating a temporary wall opposite prepared tooth surfaces using a matrix band and retainer. The Tofflemire matrix is a commonly used universal matrix that can be placed buccally or lingually. It has a head, sliding body, rotating spindle and set screw to secure the matrix band in place and contour it to the tooth. Other matrix types include Black's matrices, compound supported matrices, and the AutoMatrix retainerless system. Matrices are selected based on tooth location and cavity classification to restore anatomy and contacts while preventing excess material.