This little cardholder/wallet was designed to be safety-pinned into my pocket while thru-hiking the Appalachian trail. Lightweight, unaffected by water, and formidable, it successfully made the journey, never dropping a card or bill.
It is a flexible design, so long as you gauge it to hold the size items you want (I just wanted to fit a couple credit cards and some spare cash). I used the basket weave stitch with cotton yarn and finished it with a clay button with a little turtle painted on it.

Cast on 24 stitches
Row 1: K6, p6, k6, p6
Row 2: P6, k6, p6, k6
Row 3: K6, p6, k6, p6
Row 4: P6, k6, p6, k6
Row 5: K6, p6, k6, p6
Row 6: p6, k4, bind off 4, p4, k6
Row 7: k6, p4, cast on 4, k4, p6
Row 8: p6. K6, p6, k6

Row 9: p6, k6, p6, k6
Row 10: k6, p6, k6, p6
Repeat rows 9 and 10 four times each (total)

You should have 16 rows now in basket weave stitch.
Cast on 24 more stitches and join in round.

Round A (“row” 11): k6, p6 repeat to end
Repeat round A eight times total

Round B (“row” 19): p6, k6 repeat to end
Repeat round B eight times total

Round A (8x)
Round B (8x)
Round A (8x)

You can either bind off and sew bottom front and back in a straight line, or do a 3 needle bind-off at this point. Sew ends in and sew button onto front.