code: function() {
              if (this.useShim) {
                  YAHOO.log('Activating Shim', 'info', 'DragDropMgr');
                  if (!this._shim) {
                      this._createShim();
                  }
                  this._shimActive = true;
                  var s = this._shim,
                      o = '0';
                  if (this._debugShim) {
                      o = '.5';
                  }
                  Dom.setStyle(s, 'opacity', o);
                  this._sizeShim();
                  s.style.display = 'block';
              }
          }
docs: This method will create the shim element if needed, then show the shim element, size the element and set the _shimActive property to true
  @private
  @method _activateShim
  @static