minimum insertion lines
 

Hi, I just bought an '87 bianchi and would like an extra centimeter or two out of the seat post. The minimum insertion lines on the post are marked vertically. I am curious as to whether or not these lines can show and the insertion line is at the bottom of the lines, or is it at the top and none of these lines should be showing. I hope that makes sense. Thanks.

I'd check that the seatpost is inserted past the seat lug. That'll be about 5 cm minimum.

It sounds like you have graduation marks on the post for easy readjustment. If that's the case, the bottom mark is the minimum insertion line.

on used equipment you should always check that the post has not been cut, however, before depending on that line

I've got a bike with the min insertion line being a band of closely spaced vertical lines about 1/8" high. I assumed that they should all be hidden by the frame (if an 1/8" makes that big of a difference, I'd get a longer post to give you more adjustment).