"Walking" refers to making the reservation for dates several days (weeks/months) before the actual dates you want and then canceling a day at the begining of that reservation and adding a day at the end of that reservation until you end up with the dates you really want.
For most of the year, this is not necessary except for truly scarce accommodations (AKV CL and Value villas, BWV GVs and BW View villas, BLT Standard and TP View villas, etc.) but at busy times like Thanksgiving thru mid December, some have found success getting the dates they are looking for.