This section is from the book "School Needlework. A Course of Study in Sewing designed for use in Schools", by Olive C. Hapgood. Also available from Amazon: School Needlework: A Course Of Study In Sewing Designed For Use In Schools.
2. Draw this stitch so tightly as to bring the sides close together.
3. Make a barring exactly over the one already there, which will leave the thread at the left side.
4. Holding the thread under the left thumb, draw the needle under the two end barrings and over the thread, which will form the loop stitch.
5. Take another loop stitch in the middle of the bar-ring and one in the right hand corner.
6. Draw the needle down through the cloth close to the purl of the last loop stitch, and fasten on the wrong side.