The SOAR Telescope, near completion on Cerro Pachon - Chile, will carry Instrument Support Modules (ISMs) mounted at the two Nasmyth foci. Each ISM has three focal stations and is capable of making rapid instrument changes between them. Both ISMs also carry a Comparison Lamp System (CLS), guider and an acquisition camera, which are shared between the three instruments. One ISM supports IR instruments. The other is used for "Optical" instruments operating at wavelengths below 900nm. Beam steering mechanisms direct light from the SOAR science field or the CLS to the instrument in use. In the IR-ISM, light is sent to the lateral ports by dichroic mirrors which reflect IR and transmit wavelengths from 400-900nm to the guider. In the Optical-ISM, light is directed to the lateral ports by the use of first surface pick-off mirrors. Guiding is done off-axis. During operation, both ISMs can be rotated by 360° and must carefully control differential flexure between the guider and focal planes. A method of accurate relative flexure measurement has been developed where the ISM is rotated on its handling cart while carrying instrument mass simulators which reproduce its nominal payloads. In this paper, the ISM and its support sub-modules are described. Results of flexure measurements and tests of the CLS are provided.