The A25, A40 and A60 Series dovetail base are also available in the deeper B25, B40 and B60 Series cross sections illustrated here.
This design has the same width as the corresponding "A" Series but greater depth providing more rigidity or less deflection (2-4x the A base) of the unsupported dovetail base.	Photo 1
It also solves the problem of the knob extending below the dovetail base with "A" Models. Rather than making a plate to elevate the UniSlide, you can purchase the same model made with the B base. Replace the "A" with "B".

Photo 2: Series B60 Graduated Knob unit.
This is the preferred base to use when the full length of the base cannot be adequately supported. It is also used in a Series of Elevating Tables.

There is no B15 Series. However, consider the manual XSlide which is similar in size.

Drawing 1

Photo 3: B25 Free Sliding UniSlide with 4 sliders and 4 Traveling Slider Locks

Photo 4: Using the B base positions the payload out of the way of bottom UniSlide® Assembly. Two B2504P40 Graduated Knob models.