If it was "a simple, straight pole", then wouldn't there have only been one nail used in relation to Christ's hands/wrists? IOW, wouldn't one hand have been on top of the other hand as depicted in the picture below?
View attachment 99257
The reason that I'm asking is because scripture speaks of THE NAILS, plural, used in relation to Christ's hands/wrists and not simply THE NAIL, singular:
John chapter 20
[24] But Thomas, one of the twelve, called Didymus, was not with them when Jesus came.
[25] The other disciples therefore said unto him, We have seen the Lord. But he said unto them, Except I shall see in his hands the print of the nails, and put my finger into the print of the nails, and thrust my hand into his side, I will not believe.
The mention of "the nails" in relation to Christ's hands/wrists certainly seems to suggest that His arms were stretched out horizontally as opposed to vertically.
Since you insist........
It will help to use our brains in this one.
Before I began to really look into this, I just went along with the "T" tradition. And as I said, I really didn't, and still don't care, too much about it, one way or another. I've been a carpenter and contractor all my life, so I was asked to construct a full size cross (the typically accepted type) for a church play. I decided to build it as it would have had to have been built back in 33AD...... no sawmill cut lumber, no screws, no bolts and nuts, no glue, and no routers to easily cut notches.... and only crude, molded, square nails. I soon discovered that most of their work in fastening joints together was lashing with very crude rope.
And, more importantly, I reaffirmed something I already knew from decades of woodworking, and that is that it is nearly impossible to make an effective joint with only two pieces of wood without any of the afore mentioned assistance. That kind of joinery takes many long hours and hours of chiseling and trial fitting, then more chiseling and fitting for any such joint to stay intact while a desperate 170 -200 lb man struggles for two or three days to somehow escape this torture.
And that kind of fitting is not an "assembly line" sort of work. This has to be done independently and exclusively for each joint.
This means you cannot have a man drag a random "cross-piece" up a hill, and just slip it into a notch cut into an already set upright piece..... or even a pole lying on the ground, unset.
And this is not even considering the fact that they would not have had scaffolding to work from to get well over 300 pounds of man and "cross-piece" up into position to then begin the rather laborious and time consuming job of somehow getting those two pieces of wood fastened together way up there, at least 7 to 10 feet in the air. What would they have propped their crude ladders against? Think about it. Just not possible.
Then, you have to consider what they were doing. Simply killing a criminal. These were rough, uncouth solders, who were just intent on getting these thieves hung up to die. Just like our cowboys of the Old West... just throw a rope over the nearest tree branch, and hang the cow rustler, quick so we can get home to super.
Before any of this, you had to have lumber. (Which was not at all easy to come by, as the local Home Depot charged so much) Go Google "Trees of Israel". They just did not have access to many decent trees for making a pretty little cross out of. Remember... no sawmills in those days. No railroad cars to bring all this stuff in.... since history tells us they sometimes crucified as many as 300 people at one time.... they would have needed a lot of good poles.
Most expedient thing, stretch 'em out on a 10 or 12 foot pole, nail them down to the thing, and then stand the whole thing up, and drop the lot into a hole dug in the ground..... all done, and it only took three or four dumb solders twenty minutes, or so.
Now, if you are still having trouble with this, I would suggest only one thing. You, yourself, TRY to build a cross out of a tree you went out and cut down with an ax, (no saws in those days).... no screws, no bolts or nuts, no glue, no power tools....THEN, (and this is the tough part) tie a strong young man to that contraption you cobbled together, lift it all up (considering you are assuming the upright was not already firmly implanted vertically, waiting for your cross-piece to be installed...... giving you the easiest scenario)..... then tell the young man he gets $500 if he can twist and struggle his way off there. I guarantee you he will have your "cross" torn apart in less than a half hour... and you'll be out $500 plus the time and money you spent trying to build a "cross".
I know, because I actually tried this.