Jacket in garter stitch
You could knit in garter stitch to make a jacket instead of knitting a cardigan.
It will turn out nice and stiff if you use a smaller-sized needle. Try out a few small sample gauge (tension) squares to get the right feel. Don't worry about using a non-standard needle as we create a knitting pattern for you with any gauge (tension) at all.
While our knitting patterns so far are for sweaters (jumpers), you can easily split the front up the middle to knit two pieces - have a look at our sample sweater and see how clear the knitting instructions are. The sample knitting pattern is near the end - underneath the Buy Pattern button.
I knitted this mini-jacket as an example of what you could make. No, your eyes are not fooling you - this jacket is tiny and wouldn't fit anyone. The rib on the sleeves are only 3 rows long and I don't have any rib at all on the main body. The collar is pure stocking stitch - just 10 rows. This yarn is Aran Tweed from Studio Donegal. Any yarn works though.