All the vessels in the Mishkan had measurements in whole Amot (cubits) - 1 Amah (48-57.6cm), 2 Amot or 10 Amot, etc. The Aron (the Ark) that contained the LUCHOT (the tablets of the 10 Commandments) was the exception to this. All of its measurements were incomplete and fractured Amot. Its length was 2½ Amot, its width 1½ Amot and its height 1½ Amot. What is the reason for this? Surely the Torah, which is the most complete and self-contained entity, should be contained in a vessel with complete and not fractured dimensions.
We can explain this with 2 different ideas. Firstly, since the Torah is Divine Intellect, it is vast, endless and limitless. In Kabbalistic terms, the Torah like G-D is called EIN SOF (the endless One). Thus, it is humanly impossible for any individual to grasp and absorb all of the Torah. The most we can hope to understand will be only a fraction of it. Thus the Aron, which represents the Torah, has fractional dimensions. The more we learn, the more we will come to realize that the Torah's scope and levels of comprehension are limitless.
One can never think he has attained all of the Torah, as there are always higher levels for one to achieve. Nevertheless, this is not an excuse for one to be complacent from doing his best to understand the Torah. This is one of the reasons of why the Aron had incomplete dimensions.
Another explanation is that we all need each other in order to achieve completeness in Torah. No one on his own can perform all of the Mitzvot. We, together as a people, complement each other and complete one another. In the physical world as well, a farmer and a grocer require each other, as well as the butcher, the baker, and the candlestick maker. So too, the perfection of our spiritual world requires a collective national input.
Additionally, the Holy Ark was the only vessel in the Mishkan whose poles for carrying it were never removed, even when the Mishkan was stationary. Why? The poles represent those who support and uphold the Torah financially. Without them, the Torah, and hence the world, would cease to exist. Every piece in the puzzle is needed.