OverheadSheetColumn.PermissionID Property
The permissions ID of native columns (not created by the user) is simply the column type, such as "Mnemonics" or "Selling". This ID applies permissions to all native columns of the same type.
Non-free columns have the permissions ID constructed of several parts. The first part is the column type followed by a ":" character, such as "Selling:". The other part(s) identify the particular fields, and if multiple, they are delimited with a "\" character. For example, if the user added some return factor column, it will have the ID "SellingFactor:SOME_FIELD_ID".
Free columns (with OverheadSheetColumnKind.FreeField) and macro columns have their permissions ID set manually by the user.
The columns in user sheets (with NativeSheetType.User) are all of the type OverheadSheetColumnKind.GeneralColumn and they have no ID.
Similarly, all columns in the following sheets are of the type OverheadSheetColumnKind.NativeColumn and they have no ID neither:
NativeSheetType.Summary
NativeSheetType.CashData
NativeSheetType.Names
NativeSheetType.Wbs
NativeSheetType.Template
This property returns an empty string in such cases.