Click on the rectangle tool. Select some tiles of your choice in order to draw. Hold down the left mouse button and don’t release it. Touch one of the designer’s arrow controls while drawing. You’ll notice that the tiles drawn by this action will vanish as long as you touch the arrow control. If you move the mouse pointer aside, the tiles will be there again. However, if you release the left mouse button while hovering over an arrow control, the rectangle tool gets totally nuts.