Shorts can be defined by a model consisting of a transmission line length and a frequency dependent inductance.

Opens can be defined by a model consisting of a transmission line length and a frequency dependent capacitance.

Loads can be defined by a model consisting of a transmission line length, a shunt capacitance, a resistance and a series inductance.

Note that a sliding load can be used in lieu of a fixed load. The sliding load is based on a sliding termination embedded in an airline and the transmission line properties of that airline are used to deduce a more nearly perfect synthetic load. Because of the transmission line dependence, a fixed load is also needed at low frequencies (below 4 GHz for V connectors (shorter sliding load) and below 2 GHz for others).

Modeled as a transmission line length with some frequency dependent loss. A root-f frequency dependence of that loss is assumed.

The thru can sometimes be replaced by a unknown but reciprocal network (like an adapter or a fixture) when an actual thru connection is not practical. The accuracy will be somewhat less than if an actual thru could have been used but will be better than assuming a poor thru is a good one.