Encroaching straight Gobelin stitch
This stitch features parallel bands of satin stitch that interlock slightly into the stitches of the bands above and below. This gives a smooth appearance ideal for flat or shaded backgrounds.
For more information see the entry for Gobelin stitch.
Method
Start by making a row of vertical stitches over three threads of the canvas.
Begin the second row two threads below the first, and again make a row of vertical stitches over three threads, allowing for the encroachment of one thread between rows.
Always take the needle down into the previous row between stitches, do not bring the needle out of the previous row as this can disturb the lay of the stitches.

Embroidery Techniques
Variant Stitches
Identifying Encroaching straight Gobelin stitch
Rows of equal length straight satin stitches, each stitch impinging the previous row by one stitch resulting in an even, smooth texture.
Can be worked either horizontally or vertically.
The stitch length can be altered.
References
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Jennifer Campbell, Ann-Marie Bakewell, Guide to Embroidery Stitches (2004)