% suppose you have two vertical lines, one of height 1, located at x=0.5
% and the 2nd line of height 0.8, located at x=0.3

% to plot them:

x=[0.5 0.3];
y=[1 .8];

for i=1:2
   plot(x(i)*[1 1],[0 y(i)]);
   if i==1;hold;end
end
hold
axis([0 1 0 2])