The hammer and sear pins in 1911 can go in two ways

[hminsky]

And the right way is the big end goes on the left side under the thumb safety, or else they can 'walk' out.

Rookie mistake #3 and #4

I just had to take apart the two 1911's I replaced the triggers in, to put those pins in the right way. On the bright side, it was way faster taking them apart and putting it together this time.

 

[Rob Boudrie]

It should be obvious because the slight bevel on the pin and frame. I saw someone with the pins walking out at a match who had recently had a "professional" trigger job done. Sic'ed DanS (pro gunsmith) on him to have it fixed on the spot.