IN PREPARATION:

Open the skateboard file.
Make sure the Modeling Menu Set is selected.

CREATE A SURFACE:

Make a plane and scale it to suit you.
Give it 5 patches in both the U and V direction.\

SCULPT SURFACE:

Right Mouse Button (RMB) over plane and choose Control Vertex.
Select a group of verticies along one edge of the ramp and drag them up to begin shaping the ramp.
Re-enter object mode (either F8 or RMB|Object Mode)
Select the Sculpt Surfaces/Polygons Tool from the Surfaces shelf, open the Tool Settings, and click Reset Tool.
Change the Radius(U) to something reasonable (try 2.0)
Change the Operation under Sculpt Parameters to Pull.
Change the Reference Vector to Y Axis.
Change the Max Displacement to 2.0
The mouse icon should change to a red circle with a vector when it is held over your surface.
Drag the mouse over the ramp to sculpt it into a sweet jump.
Continue adjusting the Tool Attributes to help you do this. Also, don't be afraid to adjust individual Verticies as you see fit.

OFFSET THE SURFACE:

With the surface selected choose [Edit NURBS | Offset Surface], Reset Settings
Change the Distance to -1.0 and click Offset.
If you'd like to change the thickness of the offset, click on the second surface and find the offsetSurface tab in the attribute editor. There you'll find and be able to modify the Distance.

ALTERNATIVE OFFSET METHOD:

Look carefully at the offset surface you just created. If there are any really steep curves in the original surface it is possible after offsetting that the new surface has kinks. This may happen even if the original does not. If this is the case, delete the offset and follow these steps.
Select the surface and from the Menus: [Edit | Duplicate].
Reset Settings, set the geometry type on Instance, and Duplicate.
Drag the duplicated surface down to the desired thickness.

LOFT THE EDGES:

Select both surfaces and push F8.
In the components selection mask settings de-select Points and select Isoparms (see image)
Select two facing edge isoparms and from the menus: [Surfaces | Loft].
Do this for all four edges.

It is still possible to modify the original surface and because the offset or duplicated surface and the lofts are still linked they should all update to fit. TRY THIS - it is one of the things that makes this (and other) modeling programs so powerful.

CUTTING SECTIONS:

Turn on Grid Snap.
From the menu: [Create | EP Curve tool].
Open the Tool Settings dialogue and make sure the Curve Degree is Linear.
In the Top View draw a straint line, snapping to grid points that will be used to cut your section.
With the curve selected hold Shift and select all of your surfaces (this can easily be done in the Outliner).
Make sure you have the top view active (RMB in it) and from the menu: [Edit NURBS | Project Curve on Surface].
Move the original line back and forth and watch the projected section change as you do this.
Now, hide your cutting line and turn off surfaces in the Selection masks. Drag a window to select the section lines.
From the menu: [Edit Curves | Duplicate Surface Curves]. Reset settings and Duplicate.