They just hang around the penalty box.
They don't have a whistle and they don't have a flag.
They hold a stick that looks like a truncheon.
However, they do not use it to beat unruly footballers.
It sends a signal to the referee when something happens in the penalty box.
Some football commentators in Estonia have nicknames them 'reisisaatjad' inspired by the 'travel assistants' that were populating Tallinn's means of transport a while ago.
However, their main role is to check whether the ball has properly crossed the goal line in controversial situations. However, they are due to send a signal whenever something suspicious happens: a foul in the box or an extreme tackle that the referee might have overlooked.
Introduced as an experiment in the 2009-10 UEFA Europa League group stage, it was later extended to the Champions League 2011-12 and the UEFA Euro 2012.
After the experimental period (which was extended also in domestic leagues - Italy and France to stay within Europe) it was approved by the IFAB, the International Football Association Board which supervise on football rules and their implementation and decides over changes to the rule themselves.
Starting from 2014 Premium Liiga season, the penalty box referees will be introduced also in Estonia in an experimental way.
The first historical game having a 5th and 6th official, it will be the home debut game for Nõmme Kalju against FC Infonet in Hiiu Stadium on Saturday the first of March at 1pm.
The game will be officiated by Kristo Tohver having as touchline assistants Hannes Reinvald and Martin Lember.
The 4th official will be Sten Klaasen.
The 'new' faces, will be Eiko Saar as 5th official and Mart Martin as 6th official.
They will tie their name to the history of football refereeing in Estonia being the very first penalty box assistants.
The other three games of the Matchday 1 will feature the usual 4-man referee squad as the experiment will be limited to one game at a time for now.
Premium Liiga starts on the first of March with the following program (all times EET):
Narva Trans and Tammeka Tartu will debut on the 8th of March as Tammeka's home games have been postponed to the spring-summer when the Tamme Stadium will be available again.
Full program of the streaming of the Premium Liiga here