When the HSlider is set up with two or more thumbs there’s a gap between them always. The problem is that you may want to put them on one single value of the slider, but it’s not possible.

First: hide your thumbs

The quick solution is to make custom skin for the thumbs, setup the height and width of the thumb to be 1px and make a transparent background image for skinning them. That of course does not solve the problem. There’s still gap of 1 value between the thumbs, and still you cannot select one single value with both of them.

Make your own thumbs

It’s difficult to make the calculation and positioning of course. With that approach you’ve to be careful with the math to adjust properly the new thumbs. They can be some kind of Flex built in component. As the button control is or whatever.

Hope for workaround

As it appears there’s a reported bug for this issue. And I hope soon there will be a workaround or even better there’s going to be new version. Something I don’t like in commercial software.