What is my role in substitutions?

Under Law 6.2, the fourth official's duties include:

• supervising the substitution procedure
• checking the equipment of players and substitutes
• supervising the replacement balls

The Law 3.3 procedure you supervise:

• the referee must be told before any substitution is made
• the outgoing player needs the referee's permission to leave and must go straight to the technical area or dressing room, taking no further part
• the substitute enters only after the outgoing player has left, at the halfway line, during a stoppage, and with the referee's signal
• the substitution is complete when the substitute enters the field; until then the team may still change its choice of substitute

Under NSL Handbook Rule 14.10, the home club must provide suitable substitution boards.