If you don't have a vice... you can use a hard surface on the flat side and tap the other side with a hammer. Everyone keeps saying use the round end of a pallpeen hammer, but I used a good heavy claw hammer and had no issues. If you are putting different sized weights in each hole (inner and outer) be sure to install the shorter one first as you won't be able to aim the hammer well enough to hit the shorter one if you already have the other "taller" or heavier one in there... just some advice from the NOW informed! LOL!!! Had a hard time with my first one a while back due to this issue!