Personally I feel that the Marlin Rear ladder sight is archaic...
and I cannot understand why every new Marlin doesn't get one of their Adjustable Rear Target Sights...
Which you can purchase from Marlin or Numrich for around $10...
Here's one on My Marlin 795...screw adjust for up/down & another screw for side to side...MUCH easier to adjust, and far more precise!!!
I'm slowly changing out every one of mine...one at a time...eventually, there will be none with a ladder anymore...
Tech-sights are another, but far more expensive option if you like the M14/M16-style sights...