going from unlocked section to locked 
Locks the activeHeader as determined by which menu is open OR a header
as specified.
@param {Ext.grid.column.Column} [header] Header to unlock from the locked section.
Defaults to the header which has the menu open currently.
@param {Number} [toIdx] The index to move the unlocked header to.
Defaults to appending as the last item.
@private
function(activeHd, toIdx) {
        var me         = this,
            normalGrid = me.normalGrid,
            lockedGrid = me.lockedGrid,
            normalHCt  = normalGrid.headerCt,
            lockedHCt  = lockedGrid.headerCt,
            refreshFlags,
            ownerCt;

        activeHd = activeHd || normalHCt.getMenu().activeHeader;
        ownerCt = activeHd.ownerCt;

        // if column was previously flexed, get/set current width
        // and remove the flex
        if (activeHd.flex) {
            activeHd.width = activeHd.getWidth();
            delete activeHd.flex;
        }

        Ext.suspendLayouts();
        ownerCt.remove(activeHd, false);
        activeHd.locked = true;

        // Flag to the locked column add listener to do nothing
        me.ignoreAddLockedColumn = true;
        if (Ext.isDefined(toIdx)) {
            lockedHCt.insert(toIdx, activeHd);
        } else {
            lockedHCt.add(activeHd);
        }
        me.ignoreAddLockedColumn = false;

        refreshFlags = me.syncLockedWidth();
        if (refreshFlags[0]) {
            lockedGrid.getView().refresh();
        }
        if (refreshFlags[1]) {
            normalGrid.getView().refresh();
        }
        Ext.resumeLayouts(true);

        me.fireEvent('lockcolumn', me, activeHd);
    }