CQL 5.1
; A piece interposes to stop a check, giving check itself cql(input heijden.pgn) flipcolor { wtm attacks 1 ([rbq] K) piece $interposer in A next( move from $interposer to . attacks 1 ($interposer k) ) }

CQL 3.2
; 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.
:pgn heijden.pgn
:output Crosscheck.pgn
(position :flipcolor
; :variations
((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: