Turning A Corner. . .

. . . in Tunisian Simple Stitch is simply a matter of short rows.  And working short rows in TSS is an easy peasy thing.  For Ida (the 2014 blue blanket), ninety degree corners are needed. 

Step 1 is to make steps.  This is accomplished by working one less stitch on each forward pass.

Step 2 is to keep repeating those short rows until one stitch remains.  Notice the neat forty-five degree angle. 

Step 3 is to add one stitch to each forward pass.  On the forward pass on the "other direction" simply pick up the "end stitch" from the short row along with the last stitch of the forward pass.  So, the original one stitch becomes  two stitches on the first forward pass.  Yes, work the reverse pass in your normal way.  On the next forward pass of the TSS adding one stitch (from the short rows) results in three stitches on the needle.

Very easy.  When all short rows have been worked, there will the the same number of stitches as there were before the short rowing began and a nice tidy corner will be turned.

Ida is taking shape rather well.   You will want to know that the blue section of knit seed stitch is a chunky yarn.  The crochet TSS is a bulky.  And those two different weights of yarn play together better than I expected.

Yarn - - it's a happy thing.