When I go on vacation hold, and end vacation hold, do my posted books go from whatever postion they were at to the back of the que?

If I have a posted book, and it was #1 of say 3 copies in the system, during vacation hold the system only shows 2 copies available of that title, and after vacation hold is off, does my copy go to #3 in line or is it still #1 copy available for others? 

If you put your entire bookshelf on vacation hold, all of your books stay in their current relative position in the FIFO line. (The FIFO line is done by date/time posted, not by a number like being #4 in line). Your books stay at their original date/time posted.

If you put an individual book from your bookshelf on hold, then when you unhold that individual book, it is like you just posted it. It goes to the back of the FIFO line with a new date/time posted.

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The Wish List is different. Individual books can be placed on hold on your Wish List, and when you unhold them, you will still be at your original date/time of the Wish.

Great!  thanks for clarifying that for me.