  We investigate graphs that can be represented as vertex intersections of
horizontal and vertical paths in a grid, the so called $B_0$-VPG graphs.
Recognizing this class is an NP-complete problem. Although, there exists a
polynomial time algorithm for recognizing chordal $B_0$-VPG graphs. In this
paper, we present a minimal forbidden induced subgraph characterization of
$B_0$-VPG graphs restricted to block graphs. As a byproduct, the proof of the
main theorem provides an alternative certifying recognition and representation
algorithm for $B_0$-VPG graphs in the class of block graphs.
