# MaskingRules

> table.column to a masking rule, applied to branches before they are attached.

`table.column` to a masking rule, applied to branches before they are attached. `null` sets the column to NULL.

**Type:** map of string to string or null

## Example

```json
{
  "clients.full_name": "fake_name",
  "clients.nhs_number": null,
  "clients.date_of_birth": "shift_days(±30)",
  "carers.email": "hash_email"
}
```