Hello Jose,
Yeah, the instructions are a bit shady in that section. In step 5 there is to small graphics at the top...one square and one round....the square one is correct, the round is not. The bolt heads are to be installed on the backside of the cylinders...facing the ripper. there are two different sizes.
In this picture you can see where they go. I found it easier to make my own bolt heads, this is why they are white in the picture.
Also, I added some bolt heads to the large piston for the dozer blade! Hope this helps....have fun!!