Abstract: A matrix for making clinch-type joints between at least two members of sheet-formed material of the same or different types. Said matrix (1) has the form of a thin plate, and comprises two generally flat sheet-formed matrix elements (2, 3, 2?, 3?, 102, 103) arranged movable relative to each other so that they could slide on an essentially flat support surface (31, 34, 134) in a substantially translational or pivotal movement between a first initial position in which said matrix elements (2, 3, 2?, 3?, 102, 103) form between them at least one essentially closed matrix cavity (23, 23?, 123) and a second position corresponding to an open position for said at least one matrix cavity, said matrix elements (2, 3, 2?, 3?, 102, 103) being arranged actuated in the direction of said first position by at least one actuation means (4, 10, 104). An apparatus including such a matrix is also proposed.