....I was told that at the end of the Liturgy, after the "Upright having partaken..." I must place the Gospel book upside down on the antimension as a sign that the Liturgy if finished. It seems like an odd practice, and I have served in other churches where this is not done. Can you explain this to me?
....There is no question but that there is symbolism in the Divine Liturgy. Some of it developed out of purely practical things. The angel fans (rapide) are an example. Their original use was practical, but because of their shape and placing behind the Holy Table, they clearly open up an awareness of the continuity from the Old to the New Testament. We have discussed this before. Your question, however, is one of local custom. I will tell you how I think this custom began. Next time you finish reading the Gospel and blessing the people with it, turn and place it on the Holy Table as usual, and then take a look at it. Chances are you will be looking at the "back" of the Gospel rather than the front. It is just coincidental that, after blessing the people with the Gospel, you turn in the opposite direction and place it with the back facing outward. Then, at the end of the Liturgy, you likely will not turn it around so that you are facing the front of it. You may pick it up and place it on the antimension just the way it is standing. So the custom of placing the Gospel book upside down on the antimension at the end of the liturgy is in all likely- hood simply accidental. Since it "caught on," some people created a "symbolism" for it, and it became a "sign that the Liturgy if finished." In actual fact, it does not mean anything.