I have always used two small stitches side by side, tied together by sliding the eye end of the needle under the two stitches and over the thread, twice. Snip the thread leaving a small tail to keep the knot firm.

When drawn up firmly the knot will hold but can be undone again and the thread removed leaving hardly a trace.

I start the sewing with one back stitch and a single knot done over the stitch and the tail of the thread.

This will hold fairly loosely woven as well as fine materials.

For very loosely woven materials make two stitches in the form of an X and tie a knot in the centre of it.

Anne the Pleater