Hi. I tried to add leads on the rectangular honeycomb scattering region. I was able to add two leads (the first one is from the left from 0 < y < 10, and the second one is from the right 0 < y < 4). But when I tried add another lead on the right from 7 < y < 10, it gives an error: ValueError: No sites close to (1, 1) are inside the desired shape. Here is the code for the setup: import matplotlib.pyplot import kwant lat = kwant.lattice.honeycomb() sys = kwant.Builder() def rectangle(pos): x, y = pos return 0 < x < 20 and 0 < y < 10 sys[lat.shape(rectangle, (1, 1))] = 0 #next nearest sys[lat.neighbors()] = -1 #nearest sym = kwant.TranslationalSymmetry((-1, 0)) #from the left sym.add_site_family(lat.sublattices[0], other_vectors=[(-1, 2)]) sym.add_site_family(lat.sublattices[1], other_vectors=[(-1, 2)]) lead = kwant.Builder(sym) def lead1_shape(pos): x, y = pos return 0 < y < 10 lead[lat.shape(lead1_shape, (1,1))] = 0 lead[lat.neighbors()] = -1 sym2 = kwant.TranslationalSymmetry((1, 0)) #to the right, botttom sym2.add_site_family(lat.sublattices[0], other_vectors=[(-1, 2)]) sym2.add_site_family(lat.sublattices[1], other_vectors=[(-1, 2)]) def lead2_shape(pos): x, y = pos return 0 < y < 4 # bottom lead2 = kwant.Builder(sym2) lead2[lat.shape(lead2_shape, (1,1))] = 0 lead2[lat.neighbors()] = -1 sym3 = kwant.TranslationalSymmetry(lat.vec((1, 0))) #to the right, top sym3.add_site_family(lat.sublattices[0], other_vectors=[(-1, 2)]) sym3.add_site_family(lat.sublattices[1], other_vectors=[(-1, 2)]) def lead3_shape(pos): #tried to add this lead and gives an error x, y = pos return 7 < y < 10 # top lead3 = kwant.Builder(sym3) lead3[lat.shape(lead3_shape, (1,1))] = 0 lead3[lat.neighbors()] = -1 sys.attach_lead(lead) sys.attach_lead(lead2) sys.attach_lead(lead3) kwant.plot(sys); Thanks, James