noun
seal across two documents; tally seal
A seal stamped across the joint of two documents to prove they belong together, used in legal and administrative contexts. The 'tally' gloss refers to the same practice.
契約書の綴じ目に契印を押す。
Affix a seal across the joint of the contract documents.
契印がないと、その書類は無効になる場合がある。
Without a tally seal, the document may become invalid.