Front Post / Back Post Double Crochet (FPdc / BPdc)

Intermediate Technique

Double crochets worked around the post of a stitch rather than into its top, used to build ribbing and raised texture.

Work to the stitch where the pattern calls for a post stitch.
For front post double crochet: yarn over, then insert your hook from front to back to front again around the post of the stitch below, not through its top, so the hook goes around the entire vertical stitch.
Yarn over and draw up a loop, then complete a double crochet as normal — yarn over, pull through 2, twice.
For back post double crochet: yarn over, then insert your hook from back to front to back again around the same post, then complete the double crochet the same way.
Skip the stitch you just worked around at the top of the row, since it's now used by the post stitch, and continue in pattern.

The difference between front and back post is only which direction you approach the post from — front-to-back leans the stitch forward and back-to-front leans it backward.
Alternating front post and back post double crochet in columns is exactly how crocheted ribbing is made, mimicking knit-purl rib without any knitting needles.
Post stitches use noticeably more yarn than a standard double crochet, since the hook travels all the way around the stitch's post instead of just through its top.