how to update multi-select fields via REST API? I am trying to update a multi-select field on the bin record but getting an error and can't to figure out the correct format

{
  "memo": "",
  "custrecord_ait_bin_binlocked": true,
  "custrecord_ait_bin_itemsbinlocked": {
    "id": 56591
  }
}

{
  "type": "<https://www.rfc-editor.org/rfc/rfc9110.html#section-15.5.1>",
  "title": "Bad Request",
  "status": 400,
  "o:errorDetails": [
    {
      "detail": "Invalid value for the resource or sub-resource field 'custrecord_ait_bin_itemsbinlocked'. Provide a valid value.",
      "o:errorPath": "custrecord_ait_bin_itemsbinlocked",
      "o:errorCode": "INVALID_VALUE"
    }
  ]
}