Percentages in Card Division
This is not a convention, but a few people asked me whether I might give them some information about the percentage splits of the cards. Although this should go without saying, the percentages reflect splits in both hands (i.e., a 3-1 and a 1-3 split are the same these tables). Also, this assumes no other available information about the lay of the cards.

In the table below, the odds of a 3-2 division of 5 cards between two hands is found at the intersection of row 3 and column 2 (or row 2 and column 3) and is 67.8%
Card Division Probability Table
X 0 1 2 3 4 5 6 7 8 9 10
0 % 100% 48% 22% 9.6% 3.9% 1.5% 0.5% 0.2% 0.1% 0.05%
1 100% 52% 78% 49.7% 28.3% 14.5% 6.8% 2.9% 1.1% 0.4% 0.1%
2 48% 78% 40.7% 67.8% 48.5% 30.5% 17.1% 8.6% 3.8% 1.4% 0.5%
3 22% 49.7% 67.8% 35.5% 62.2% 47.1% 31.3% 18.9% 9.5% 4.2% 1.6%
4 9.6% 28.3% 48.5% 62.2% 32.7% 58.9% 46.2% 31.8% 19.1% 9.8%
5 3.9% 14.5% 30.5% 47.1% 58.9% 31.2% 57.2% 45.8% 31.9%
6 1.5% 6.8% 17.1% 31.3% 46.2% 57.2% 30.5% 56.6%
7 0.5% 2.9% 8.6% 18.9% 31.8% 45.8% 56.6%
8 0.2% 1.1% 3.8% 9.5% 19.1% 31.9%
9 0.1% 0.4% 1.4% 4.2% 9.8%
10 0.05% 0.1% 0.5% 1.6%

If you want to find the probabilities for the distribution of 3 hidden hands, I would recommend you look up Mathematical Tables in The Official Encyclopedia of Bridge (Henry G. Francis, Alan F. Truscott, eds.).