A device that helps to properly align and install large pistons in cylinders is disclosed. Large pistons and cylinders are heavy and difficult to handle, and if the piston is not inserted in the cylinder perfectly in line with the length of the cylinder, damage results. The device holds both the piston and cylinder being assembled, and has a number of alignment mechanisms. A laser is also used to set up the device and to ensure that the piston is straight with the center line of the cylinder for proper alignment and insertion.