The invention is a modular terminal block assembly. The modular terminal block assembly includes a base module in which communications company lines may be dressed and retained during the dressing operation. A connector module is provided for attachment over the base module and to engage the distribution lines retained in the base module with insulation displacement connectors (IDC) which are retained in the connector module. A protection module is provided for engagement with an opposite side of the base module so that protection can be provided on the lines without interfering with the connection termination of customer service line on the connector module. The modular terminal block assembly provides structures which allow the assembled modular terminal block to be retained on a standard U-shaped mounting frame or for attachment to a rod frame system. The protection module maintains protection on the lines while the terminal block assembly is in contact with the U-shaped frame and rod frame system. A half-tap assembly may be attached to the modular terminal block, independent of the service line assembly for the addition of a line to the terminal block. An environmental protectant is retained in the modular terminal block to protect the conductive connections retained therein from detrimental environmental effects.