Do sewing machines need access to both sides of the cloths?

Unlike sewing by hand, where a needle is put through one side of the fabric, down and up the same side; making a stitch on both sides of fabric using one thread, sewing machines basically make a series of "loops" one on each side.

The top thread which comes through the needle , loops through the bobbin thread which comes up from below to make stitches. So in essence the sewing machine does have access to "both sides" of cloth.

Candide

The blind hem machines need only one side. Why is that important to you? Perhaps with some more background on what it is you are attempting to accomplish we can assist you better.

There is an animated illustration of stitch formation at