Memoir: Margins vs Marginsandblock

Question

I am using Memoir and try to setting up the pagelayout but it don't matter how often I read section 2.4.2 I don't really get what is the difference between using

\setlrmargins{spine}{edge}{ratio}

and

\setlrmarginsandblock{spine}{edge}{ratio}

Can anyone explain in simple words what the excat difference is?

In my institue I have just the requirements of using this:

• up marign: 2-3cm
• down margin: 2-3cm
• inner margin: 3-4cm
• outer margin: 2-3cm

I just use oneside instead of twosided.

Edit: There is a good exmaple an pages 10-11 in the manual of the pagelayout and its features, however for me this is more confusing than helping

Answer 1

As it says in the manual (section 2.4.2):

\setlrmargins sets the left and right margins, assuming that both the page width and the typeblock width are already fixed. That means the space available for both margins together is also fixed, so there are only a few useful combinations of the input parameters, otherwise you are either over-specifying what you want, or your specification is inconsistent with the page and typeblock widths.

\setlrmarginsandblock sets the left and right margins and the typeblock width assuming that only the page width has already been fixed. Since this option sets three parameters in the page layout not two, more of the possible combinations of parameters make sense.

Tables 2.4 and 2.5 show what this means, for every possible combination of input parameters.

If you want to set both margins to given sizes, then the textblock width can be calculated (as page width - left margin - right margin) so you want to use \setlrmarginsandblock.