Bar on the anl fuse block?

[cheese22]

Probably a question with a simple answer.  On the anl fuse blocks, the posts that connect to the power wire from the battery is always a bar.  Meaning, no matter how many posts on the outgoing side of the block, they are all individually fused.  On the input side, it seems that the block could be fed by one large cable.  So, why are there as many posts on the input side as there are on the outgoing?

[audiofanaticz]

Correct.
The reason for so many is due to some people using multiple runs of power wire from the front of the vehicle to the back.
In my truck for example I have 9 positive runs of 1/0 and 9 negative runs of 1/0 (18 total) coming from my 3 alts under the hood to the back batteries.
So when people have larger systems with over 1600amps worth of alternator charging, multiple 5,000+ watt rms amps, etc one single run of 1/0 or even 4/0 coming from under the hood simply cant handle the current load. 
Now take into consideration of the length of said wire which reduces its current rating, resistance and voltage drop in the wire, hell even if you're pulling the maximum current limit from whatever wire you're running your going to have to factor in heat and even more resistance. 
So that is why there's multiple spots for additional wires to be connected so you can adapt to your needs and overcome obstacles and restrictions in the wire.
Hopefully that helps.