There is a big difference between county jails (where people serving less than a year go), various state prisons and federal prisons.
I have visited in 4 different federal prisons. Their security is similar to the TSA screening at airports. You fill out a form listing various types of contraband and have to check no, beside each. Then you send shoes, belts, wallet, and metal things etc. through an x-ray machine. Then you walk through a metal detector.
If you alarm the mental detector, you get wanded. Women wearing an underwire bra are not allowed in unless they take it off. There are also several random protocols, such as every 5th male receives a patdown, or every third female is swabbed for drugs or gunpowder.
Of course you must present a driver license or other government ID. I'm MTF, and my driver license says male. I was pretty uncomfortable when they called a male correctional officer to do a random patdown.
As long as your binder has no metal parts, and you wear a looser shirt over it, you should have no problems. They just don't want female visitors wearing skimpy, revealing, sexy clothes.
Example of federal visiting rules here:
https://www.bop.gov/locations/institutions/spg/SPG_visit_hours.pdfHere's an example of screening rules.
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Screening: Visitors will be required to successfully pass through the walkthrough
metal detector. In the event this is unsuccessful, a hand-held metal
detector will be used to identify the location of the metal and it is the
responsibility of the visitor to remove that item from the area. In the event the
visitor can not remove the item or they suspect the item is a part of their clothing
such as buckles, straps, hair pins, bras, etc... they are responsible for departing
the institution and rectifying the issue. All visitors are required to clear the walk
through metal detector without exception.
Visitors with medical devices that cannot be removed must have supporting
documentation from a physician.
Should the visitor still be unable to successfully pass screening, the Operation's
Lieutenant will be contacted for further assistance. No visitors will be allowed
entrance without clearing the walk thru metal detector.