The installation has a portal or gateway to another dimension or dimensions. This can range from an otherwise innocuous-looking door to a humming high-tech portal surrounded by support equipment and monitors. The portal provides two-way travel to and from the other dimension, and it may even reach a number of related dimensions. At the GM’s discretion, an appropriate skill check—typically Expertise or Technology—may be required to operate the portal.
D20 Hero SRD Installation Article- http://www.d20herosrd.com/7-gadgets-gear/installations