To allow the opposing king a flight, a line-piece moves across a critical square so that a second unit can temporarily occupy that square and thereby create a shut-off (subsequently moving away from the critical square).
Alias: Helpmate Indian theme.
The Chess Monthly, 1860 (version)
Maroc Echecs, 2019
Meinking, Daniel E.
F. Abdurahmanovic-60 JT, StrateGems, 2000
Rehm, Hans Peter
Schach-Echo, 1st Prize
The Problemist, 2000