4.1 Staff employed at screening checkpoints need to be carefully selected following stringent requirements and adequate training implemented by the appropriate national authority. At a minimum, a screening checkpoint should be staffed by the following:

• Travel document/ticket checker: located at the entrance to the screening checkpoint, makes sure only ticketed passengers enter the screening area. Should also make sure that passengers are at the right location. These staff members should be trained in passenger risk assessment to identify which passengers should be subjected to increased screening measures. Training for these staff members does not need to be the same as screening checkpoint employees. Moreover, they can be employed by a different (often the air carrier) organisation than screeners.

• X-ray loader: makes sure baggage is appropriately loaded on the conveyor belt. Will also make sure that all electronic items (laptop computers, cameras, etc.) are removed from main carry-on baggage and put in another container for screening. Will also ask passengers to empty their pockets of loose metal articles.

• X-ray operator: reads the image projected by the X-ray machine and selects bags for searches that may cause a concern due to prohibited contents or unclear images. The X-ray operator should not stay in his/her position for more than 20 minutes.

• Bag searcher: manually searches the bags signalled by the X-ray operator. The number of X-ray operators/bag searchers should be such that a rotation can be performed without slowing the screening process.

• Passenger searcher: the number of searchers should be dependent on the passenger flow but there should be at a minimum two people, one of each gender. They are responsible for secondary screening of passengers who trigger the WTMD.

• Explosive Trace Detection equipment operator: Responsible for swabbing baggage highlighted by the X-ray operators for explosive trace components.

• Supervisor: Responsible for the overall efficiency of the screening checkpoint. Should not get involved with the operation of the screening equipment.
https://www.icao.int/SAM/Documents/2008/AVSECPAXBAGTF1/PAXBA...

Each machine has a team of seven – the pacer, who directs the visitor; the loader, who fills the trays; the screener, carefully watching the x-ray images; the bag searcher; the body searcher; the team leader; and the worst role, "tray bitch" – gathering up the trays at the end of the conveyor belt.
https://www.theguardian.com/business/2012/jul/23/g4s-trainee...

And see also the references to "loader position" in https://www.iata.org/whatwedo/security/Documents/smart-secur...

https://www.asi-mag.com/life-in-the-fast-lane/

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Note added at 1 day 18 hrs (2019-02-16 15:33:23 GMT)
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@Michael: you're welcome :-).