Hi,I have just built the metcalfe signal box,they give you a choice of brick or stone.The part you dont use they tell you to discard,don't it comes in handy for the inside.Cut to fit with the plain side in and they line up with the widows,the only part I had to make up was across the back wall.I then printed off some brown and cream paper and covered them then fitted in place(the cream was pale yellow but looks the part).The brown came up to the bottom of the window cills,just got to fit the light,and put the signal man on to his chair,hope this helps Jim