thank you very much. I call cic.gc.ca . the standard answer is:
Thank you for contacting Citizenship and Immigration Canada. I am pleased to follow up on your request:
Validating a Confirmation of Permanent Residence at a Land Border (Flag Pole Procedure)
Once you get your Confirmation of Permanent Residence (IMM 5292 or IMM 5688) from a Canadian visa office and, if necessary, your permanent resident visa in your passport, you must have these documents validated by an immigration officer at a port of entry. If you did not see an immigration officer when you arrived in Canada and are still in possession of your IMM 5292 or IMM 5688 document, then you must:
Go to the American land border and explain to the officer that you do not want to enter the US; but that you want to return to Canada immediately to validate an immigration document (this is called the flag pole procedure).
Once at the Canadian border, you must show the officer:
your passport, travel or identity document (including secure visa counterfoil (IMM 1346), if applicable); and
your Confirmation of Permanent Residence form and instructions issued by the Canadian visa office; and
your proof of legal status in Canada, such as a valid work permit, study permit, temporary resident permit, or visitor document; or
any immigration document in your possession (whether valid or not); and
proof of implied status (if applicable), for example:
payment receipt;
copy of your application;
printout of online application;
proof of mailing.
To find the land border closest to you which offers immigration services, please visit the Canada Border Service Agency Web site