A piece of thin nylon rope with a bit of wood tied on each end. Put the seal on the window, push the rope into the seal where it would fit the body, sit the windaow against the body with a helper keeping it in position. Remembering to keep the rope on the inside. Then pull the rope, this feeds the rubber seal onto the body. You will also need to put some windscreen sealant on the seal, (not silicone).