My gap was left at the top.

When the floor isn't level (and it's never level), there has to be shims between the cabinets and floor to achieve that level. The toekick is then installed to the floor so you don't see that gap. The gap ends up where you can't see it unless you are on your hands and knees. If it's out of level significantly, then I usually include a tall skin and the installer custom cuts toekick at the angle needed for coverage. It's a higher labor and materials charge to do that, and that's why it's only done when there is a bigger gap.

We typically scribe them in so that they are snug, only time that we do leave a slight space is if we are using leg levelers so that the kick is removable...makes it easier to pop of the base if there is a gap at the top

I would definitely not want a gap there. I have two dogs that constantly shed and often there are large tumbleweeds of fur in the toe kick area. I would hate to think of that fur getting through the gap and living under my cabinets. By closing the gap at least the fur would remain in a place where it can be swiffered up.

I am a KD and I agree with what LWO said. Only thing I will add is, I am thinking about starting to order the 'handicap' toekick boards (8-9" tall) from now on as this is common customer complaint. However, that toekick material is more expensive and the labor to scribe it to fit and install it is also more money. Most people do not want to pay that extra. And not all cabinet lines offer the taller toekick or custom toekick board height. In that case, as LWO stated, you would need to order paneling....and that would be a lot more expensive. So it could cost $20-$30 more per length of toekick plus labor expenses. Overall could cost $200 to $300+ more depending on materials needed to order..

We used semi-custom cabinets and the toe kick came in only one height. Since our kitchen is open to the great room, you could see the gap that occurred at the top of the toe kick due to the floor not being level. We used a piece of scribe molding to cover the gap. I got Home Depot to match our cabinet color (using a scrap of crown molding) and painted the scribe molding.

We recently completed a kitchen remodel and discovered the same space between toe kick and cabinet. We also have never had this in any of our other kitchens. As one of the commenters stated, it is a perfect space for pet hair to float. Also, spiders to find a safe space to gather and dust to settle without the ability to ever clean out. We will share dovetonsils solution with our contractor. Any other remedies out there?