There are 7797 scops for sandwichs (folds #1~#42) in my DB.

after I analysis 30 scops, I got these conclutions:

S1 will belong to one sheet, S2 will belong to another.
S2 will connect to the last Strand.
this is the start and the end strand, they are in one edge of the sandwich, and used for connect two sheets.
the other side of the sandwich are connected by a loop.

only found one exception ([88535]1cd0A), but kind of acceptable.