DGF
Vertex        % the vertices of the grid
-1   -1       % vertex 0
-0.2 -1       % vertex 1
 1   -1       % vertex 2
 1    -0.6    % vertex 3
 1    1       % vertex 4
-1    1       % vertex 5
0.2  -0.2     % vertex 6
#
SIMPLEX       % a simplex grid
0 1 5         % triangle 0, vertices 0,1,5
1 3 6         % triangle 1
1 2 3         % triangle 2
6 3 4         % triangle 3
6 4 5         % triangle 4
6 5 1         % triangle 5
#
BOUNDARYSEGMENTS
2   1 2       % between vertex 1,2 use id 2
2   2 3       % between vertex 2,3 use id 2
4   3 4       % between vertex 3,4 use id 4
#
BOUNDARYDOMAIN
default 1     % all other boundary segments have id 1
#
# examplegrid1s.dgf
