A modular DIN rail terminal block forming electrical connections between a number of wires and a circuit board mounted on the block, the block comprising: a stack of modules, said modules stacked together side-by-side to form the modular block, each module including: a contact body, a plurality of wire contacts on one side of the contact body, a plurality of pin contacts on the opposite side of the contact body, leads in the contact body extending between the wire contacts and the pin contacts, and a first circuit board support on the opposite side of the contact body, wherein the modular block also comprises a DIN rail latch on the bottom of the modular block for engaging one flange of a DIN rail supporting the module, characterized in that each module includes: an extender body, a second circuit board support on the extender body, an interfit connection in the thickness of the module attaching the extender body to the contact body below the circuit board supports, the interfit connection including a head on one body fitted in an opening in the other body, and DIN rail projections on the bottom of the extender bodies facing the DIN rail latch for engaging another flange of the DIN rail supporting the terminal block; wherein each contact body has a fixed dimension along the module and each extender body has a selected dimension along the module dependent upon the size of a circuit board on the board supports. a stack of modules, said modules stacked together side-by-side to form the modular block, each module including: a contact body, a plurality of wire contacts on one side of the contact body, a contact body, a plurality of wire contacts on one side of the contact body, a plurality of pin contacts on the opposite side of the contact body, leads in the contact body extending between the wire contacts and the pin contacts, and a first circuit board support on the opposite side of the contact body, wherein the modular block also comprises a DIN rail latch on the bottom of the modular block for engaging one flange of a DIN rail supporting the module, characterized in that each module includes: an extender body, a second circuit board support on the extender body, an interfit connection in the thickness of the module attaching the extender body to the contact body below the circuit board supports, the interfit connection including a head on one body fitted in an opening in the other body, and DIN rail projections on the bottom of the extender bodies facing the DIN rail latch for engaging another flange of the DIN rail supporting the terminal block; wherein each contact body has a fixed dimension along the module and each extender body has a selected dimension along the module dependent upon the size of a circuit board on the board supports. an extender body, a second circuit board support on the extender body, an interfit connection in the thickness of the module attaching the extender body to the contact body below the circuit board supports, the interfit connection including a head on one body fitted in an opening in the other body, and DIN rail projections on the bottom of the extender bodies facing the DIN rail latch for engaging another flange of the DIN rail supporting the terminal block; wherein each contact body has a fixed dimension along the module and each extender body has a selected dimension along the module dependent upon the size of a circuit board on the board supports.