Their decisions can change the course of a game, capable of plunging cities and even entire countries into a toxic mixture of despair and rage (sometimes replaced with joy and relief when the outcome is more favourable).
Not without good reason does one squash website describe refereeing as a "thankless but necessary task." Indeed, is squash the most difficult sport in the world to officiate?
Championship referee John Massarella of England, the man in charge of the squash refereeing system at the Commonwealth Games, seems to think so.
"There are so many decisions in squash, probably more than in any other sport where a referee can be called upon," he said.
"The length of a match is undefined because it's best of five in singles and best of three in doubles. If a match lasts an hour, sometimes you can be called upon to make 50 decisions, which is quite a lot of concentration."
Many of those decisions involve simpler rule breaches. When serving, a player must hit the ball above a service line a little above head height in the front wall of the court, and thereafter above an out-of-bounds zone at the bottom of the wall, known as the "tin", which varies in height for men's and women's singles and doubles tournaments.
The ball cannot strike the side walls above a diagonal cut line reaching up to the top of the front wall, nor can it bounce on the floor more than once.
However, the referee's job is often most difficult when less clear-cut matters are at hand.
"A lot of the decisions are interference - whether the incoming player or the outgoing player from the ball is causing the play to stop," John said.
"If there's an interference an incoming player sometimes can't get to the ball because the outgoing player hasn't moved sufficiently. On occasions the incoming player is not taking a direct line to the ball."
Referees are regularly called upon to decide what constitutes such an obstruction, which if ruled to be so results in a 'let' - where no stroke is awarded and the point is replayed. More serious offences are punished with the award of a penalty stroke.
Perhaps thankfully given the sheer pace of squash, referees do not have to act alone. Three referees preside over a match, one each covering the left, centre and right of the court.
John explains how the system works: "Each referee has a card, and they give their decision pointing it towards the centre referee, who then collates the decisions and gives the majority or the unanimous decision.
"If the two side referees give a different decision to the central referee, he has to give their decision. But the control, the management and whatever in the match is down to the central referee, his is still the last say."
The card in question has four lettered corners, each representing a decision - "G" for "Good", "N" for "N Good", "L" for "Let" and "S" for "Stroke". The reverse side of the card is blank, meaning the players cannot see through the glass back wall what each individual referee has given.
In the show court of a tournament one video review is also granted to each player per game if they are unhappy with the decision of the three referees - although the officials themselves cannot opt to review a play themselves.
How does refereeing squash compare to refereeing football?
"A good friend of mine 10, 15 years ago was a top-line football referee, and he said that he felt the major difference where the football referee had the advantage is the referee could get into the right position himself to see the decision properly," John said.
"As a squash referee, we have various different positions, but we are in that one position. Depending on how the show court is situated you can be in the crowd six or eight rows back. The trajectory can be flat, the trajectory can be high, you can be far back - but you've only got that one position, and sometimes it's difficult to see clearly.
"The concentration levels are massive. There's something happening so often, if you're distracted, you've just lost the moment and lost the situation, and that is really where the better referees come through in the end with their levels of concentration. If you just see something that distracts you, you must keep focussed."
So when you turn up to the squash competitions at Scotstoun later this summer, spare a thought for the men and women with perhaps one of the most difficult jobs in sport. Rather them than me.