I can't find the fuse box in my 03 Isuzu ascender. book say rear seat under. there is no way to get under the rug. the 2 roll there a box under seat that we can get open w/out removing the whole seat.

There are 2 fuse boxes. One in the engine compartment right next to the battery. The other one is indeed under the seat. You must pull the fabric tab in the middle of the seat and pull it towards the drivers seat. The entire seat bottom will lift up towards the drivers seat. Your rear seats fold down if you didn't know that already, seat and back rest both.