; Crosscheck.cql,  Created by Peter Boll.
; One side counters the other side's check with interposing a piece onto the checking line and gives check.
(match
:pgn heijden.pgn
:output Crosscheck.pgn
(position :flipcolor
; :variations
:sequence
((position :check :moveto .??)
(position :check :moveto .??) 
)
)
)

This cql finds 1824 studies with such a moment in the Harold van der Heijden database V 2015. 

Here a few examples are showed: