The Willis ramp very cool feature that's been incorporated into this bass.
The custom shaped ramp enhances the
feel and the sound of the bass.

Here's how it works:
Most bassists like to play over the pickup.
It's a combination of having a place for your thumb and the feel of having something under your fingers. Playing only over the pickup will get you a nice punchy mid-range sound, but moving your hand around will allow you to get other types of sounds.

Playing closer to the neck (even only an inch closer) will produce a fuller sound.
Playing next to the neck will let you get very full-sounding melodic notes that don't happen when you only play over the pickup.
Without a ramp, any position other than over the pickup feels less secure, kind of like a "no man's land".

The surface of the ramp and the custom Bartolini/Willis pickup (manufactured only for this bass) are contoured to the fingerboard radius, so that you can play anywhere from over the pickup to right next to the heel of the neck and the "feel" for your right hand will be exactly the same.

Another reason for the ramp is to get your right hand to produce the best sound.
Here's how it works: The more force you use to play a note on electric bass, the more the tone suffers.
Playing hard will generate a big gnarly attack, but that just creates a bigger difference between the attack and the volume where the string wants to settle in and vibrate:
note played hard
creates louder attack
but quicker decay

Turning your amp up and playing softer will still make the speaker act as if there was a big attack, but the note that follows immediately afterwards will be much louder, have more fundamental and sound bigger for a much longer duration. This especially true for a fretless:
with amp turned up
speaker reacts the same,
but the sound stays louder with more fundamental, lasts longer

A properly set up ramp prevents "digging in" too hard, while still allowing you the full range of dynamics that become available by playing softer. To get the most out of your bass and the ramp, use the steps outlined in the setup instruction manual to set up your bass.