Again, I am working "blind" here - so my advice may not be on the mark.
What I have been talking about is when you "knit on" an edge to a body of work. As I said, normally it is joined at every other row as you knit the last stitch of the edge row is worked with one stitch from the body (as if it were a decrease) - depending on the pattern this may be a purl2tog, k2tog, skp, ssk....
At the corners you need more rows of the edge to ease around the corner. There are two really basic methods to do this
a) on two or more consecutive return rows of the edge the last stitch of the row gets worked together with the SAME stitch of the body.
b) on alternate return rows the last stich of the edge is worked without joining to the main body - thus doubling the number of edge rows per stitch worked on the main body of the knitting.
With either method it is usually done for a number of stitches on either side of the actual corner. If the edge repeat (for example) is 8 rows, it would not be uncommon to do this for 4 stitches on either side of the corner. Normally those 8 stitches would be two repeats of the edge pattern, but because of the ease you are building in it will take 4 repeats of the edge pattern to go around those 8 stitches.