To hold the shaft from turning, we used heavy twine sprayed with spray adhesive that we wrapped around the shaft. Then as shown in the video on AppliancePartsPros.com, we used a screwdriver and hammer to hit the old rubber coupler in a clockwise direction to break the threads free. Then after removing the string, we simply started the new coupler on the shaft threads, turning it counter-clockwise. Finally we positioned the blender jar and powered up the unit to fully seat the new coupler.