noun
seal across two pages; tally impression
A seal stamped across the edges of two adjoining sheets of paper so that the impression spans both, used to verify that the pages belong together (e.g., in contracts or official documents).
契約書の綴じ目に割印を押す。
Affix a seal across the binding edge of the contract.
割印がないと、その書類は無効になる場合がある。
Without a tally impression, the document may become invalid.
契印 is a similar seal used specifically on contracts to prevent forgery, while 割印 is a broader term for any seal spanning two pages.
Compound of 割り (wari, 'splitting') + 印 (in, 'seal'), referring to a seal that is split across two pages.