# set terminal pngcairo  transparent enhanced font "arial,10" fontscale 1.0 size 500, 350 
# set output 'key.5.png'
set key at 0, 0, 0 right bottom vertical Right noreverse enhanced autotitles box linetype -1 linewidth 1.000
set key noinvert samplen 0.2 spacing 1 width 0 height 0 
set arrow 1 from -3, 0, 0 to 3, 0, 0 nohead back nofilled linetype -1 linewidth 1.000
set arrow 2 from 0, -3, 0 to 0, 3, 0 nohead back nofilled linetype -1 linewidth 1.000
set title "Key (<manual> vert bot right)" 
plot x,-x