Splice joints are applicable to two rolled or welded I or H identical cross-sections, or whenever the internal depth is equal (this is the total depth minus twice the flange thicknes and minus twice the corner radius).
The first typology (Sh1) has one plate only on each flange.
The second typology (SH1) has bolted plates and backing plates and it is applicable only whenever the two cross-sections are identical (rolled or welded).
Typology Sh2 is used for similar but not identical cross-sections. It is only necessary that the new web depth is equal (couples HEX-HEY, with X not equal to Y and X and Y equal to A, B, M, AA, etc.)