Is there a way to extrude an object or shape along a path/curve, so you get a solid object? For example, a rectangle shape along a curve to get a long bendy sidewalk.
I feel this was in an older version of blender, but I can't find it now.
Use a bevel object in the curve properties > Geometry panel.
You can use any curve to define the cross section of another curve. Make sure they are in separat objects because the object origin of the cross section curve will be extruded along the main curve. As you can see, you can put all kinds of independent curves into the Bevel Object
The Merge option merges duplicate vertices so that the resulting object stays as one mesh.
Note that when using the Fit Curve option in the array modifier, you may have to apply the scale to ensure this works correctly (CtrlA> Scale).