Phill,

Gate starts work by using one boat in the fleet (usually the 4th boat to finish the previous race) to open the start line by sailing along on port protected by (usually 3) power boats; one in front; one to leeward and one behind which is the end of the line.

The gate boat sails past the pin end of the line and then sails on port upwind opening the gate; the gate boat (and protective power boats) have rights and all other boats start on stbd having ducked the stern of the gate boat. The boat sails for a pre-defined amount of time and then is released to sail on (the gate boat does not need to cross the line).

The tactics for a gate start are different. It can depend on who is the gate boat (as they control the speed it opens), if the gate boat on a lift (thus good to wait till later), or Header (start early); is the gate boat sailing into foul tide (start early); or into good tide (start late). Etc…