Tunisian simple stitch and variants all work the front vertical bar of the stitch.
Tunisian Simple Stitch (Tss)
Insert hook from right to left behind front vertical bar. YO and draw up a loop.
Tunisian Simple StitchTunisian Simple Stitch
Modified Tunisian Simple Stitch (Tmss)
Tmss gives a similar look to Tss, but it creates a flatter fabric. Insert hook from right to left behind front vertical bar AND under front horizontal bar. YO and draw up a loop.
Modified Tunisian Simple StitchModified Tunisian Simple Stitch
Twisted Tunisian Simple Stitch
Another variation on the simple stitch is made by inserting the hook from left to right. When you insert the hook this way there are two was to twist the stitch - up and down - and the two stitches look very different.