Iceland theme
A line is controlled from opposite directions by two black line-pieces of the same motion. Black interferes with the line on both directions, and consequently White can give mate on a square on that line.
Paros, György
Die Schwalbe, Carte de Voeux TT, 1949
h#2 2.1... (5+9)
1.Sc4
Kd1
2.Bg4
d4#
1.Sg4
Kf1
2.Bc4
f4#
Zarur, Almiro Elias
Dalla Rosa JT, 1964
1st Comm.
h#2 2.1... (5+10)
1.Sfe2
Sgf4
2.Se6
Se3#
1.Sfe6
Sdf4
2.Se2
Se3#