I googled "stretcher bars" and was told that they are used by artists to stretch their canvas so I wouldn't think they would be good for stitching.....not comfortable to hold at all.

These stretcher bars are made for needlework....counted canvas or needlepoint. They are finished smooth so as not to snag fabric or threads.

You can hold them and stitch one-handed if they are not too heavy or cumbersome. Most Stitchers use some kind of a clamp on a table, lap or floor stand to hold them.