Father Lawrence:
The position of the Church Fathers has always been that four nails were used and that His feet were nailed to a board which was then center nailed to the perpendicular of the Cross itself; this is so firmly entrenched in Orthodox Iconography as to render the traditional Orthodox Cross as having 3 bars, the top bar being the sign, the middle bar being the horizontal on which His hands were nailed, and the bottom bar being the foot board. Holy Tradition says that at the moment of His death, his legs went into spasm causing the board to be forced up on the right and down on the left, creating a diagonal direction of the foot board and, at the same time, showing the Judgement of the two thieves, the one on the right inheriting Paradise and the one on the left condemning himself to hell.
As for the Shroud of Turin, the Church has no official position on it; however it would be impossible to say whether one or two nails were used, since a single nail would have still be driven through both feet even if only one was used. Depending on how His legs were positioned when the shroud was placed on him, would determine if one or two blood spots would be present at the feet. Finally, we must remember that nailing was not commonly done as a part of crucifixion by the Romans; it was used in very large men whose weight made roping them to the cross impractical, and to heighten the torture of crucifixion, to prolong the agony, since by supporting the limbs, in particular, the legs with nails, the death, which ultimately occurred as a result of slow suffocation of the body from its weight hanging on the cross, was prolonged.
