The steps in the rating scales of two test forms, or in the item bank and in the current form, can be anchored at their other form or bank values. Then the common rating scale calibrations are maintained. If you wish to force category 0 to stay in an analysis, anchor its calibration at 0. 0,1,2,3 and this particular scale is to be anchored at pre-set calibrations. By default, the pivot is placed at the point where the highest and lowest categories of the scale are equally probable.
Pivot anchoring redefines the item difficulties.
The item difficulties are to be centered on those pivots. If agreement is wanted, pivot between 3 and 4, identified as step 4. If no disagreement is wanted, pivot between 2 and 3, identified as step 3. 3.