Yep, that pin goes in from the top, and it is retained in the frame by the safety detent mechanism. That pin retains the hammer pivot pin, keeping it from working out during shooting. Ask me how I know!
Ok, I'll bite.
"How do you know, Rock-it?"
I know because I had a gunsmith who knew nothing about working on CZ pistols install a new trigger for me. I could not get the trigger pin out, so I took it to a local gunshop, and they had their gunsmith do the work. Well, for some reason, the smith decided he needed to remove the sear cage assembly from the frame in order to put a new trigger in, and he lost that pin. The next time I was at the range shooting that pistol, after about 50 rounds or so, I felt something poking into the base of my stronghand thumb. I stopped shooting and looked at the pistol, and the trigger pin was backed about halfway out of the frame. Darn good thing my grip was nice and high.
That's not the end of the story either. The reason I say he knew nothing about CZ pistols is not because he lost that pin. The reason I say that is because in attempting to get the sear cage out, he did not lift the leg of the sear spring out of the slot in the safety lever shaft, but apparently just hammered hard enough on that shaft to shear off the leg of that spring right at the edge of the hole that the shaft fits through. And, he scratched the finish on the outside of the frame while banging on the safety shaft. The scratches were the first thing I noticed when I got the gun back, but the shop owner denied that the smith removed the sear cage, and said the scratches could not have been made by him. When the hammer pin started to work out, then it was confirmed in my mind that he had indeed taken the sear cage out. There is no way to lose that little retainer pin with the sear cage in place. Needless to say, I won't take anything back to that smith. I still use the shop, because after showing him the evidence, he bought a new spring and pin for me.
That's my story, and I'm sticking to it.
