Size - 4 years

Materials - 2 skeins of Phildar Exotic, 90m per 50g. Any other flat ribbon yarn that knits to gauge. 1 pair of 9mm needles. 2 buttons to fasten straps to back of tank.

Measurements - length from bottom to arhomes = 25cm width = 23cm

Gauge - 16 stitches and 17 rows over 10cm stocking stitch with 9 mm needles

Directions.

Using 9mm needles and Exotic yarn cast on 71 stitches.

Row 1 - Knit
Row 2 - Knit
Row 3 - Purl

Repeat rows 2 and 3 working in stocking stitch until work measures 25cm or the length you desire to armhole shaping ending with a purl row.

Shape armholes - cast off 20 stitches at the beginning of the next 2 rows. (31 stitches remaining)

Next row - K1, K2tog K to last 3 stitches, SSK, K1 (29 stitches)
Next Row - Purl to end
Next row - K1, K2tog K to last 3 stitches, SSK, K1 (27 stitches)
Next Row - Purl to end
Next Row - K1, K2tog K7 SSK K1 Cast off one stitch K1 K2tog K7 SSK K1 (22 stitches)

Working on 11 stitches only complete neck shaping for first side.

Next Row - Purl to end
Next Row - K1 K2tog K to end (10 stitches)
Repeat the above 2 rows until 6 stitches remain
Work in stocking stitch until straps measure 26cm from beginning of V neck shaping or desired length. Break yarn leaving about 10 inches and place the strap on scrap yarn and work on the opposite side

Next row - Rejoin yarn to 2nd neck side and purl to end.
Next Row - K to last 3 stitches, SSK K1
Repeat the above 2 rows until 6 stitches remain
Work in stocking stitch until straps measure 26cm from beginning of V neck shaping or desired length.

If you can persuade your child recipient to stand still for a fitting at this point it will make life much easier. Alternatively measure against an existing tank to ensure straps are required length. (note if you do not want the straps to cross over but to go straight across the back make the straps shorter.
Continue knitting the straps until they are exactly the desired length. On the following knit row work a buttonhole in the middle of the strap. I always just make an eyelet by using y fwd K2 tog.
Work another 3 rows in stocking stitch before binding off.

Complete 2nd strap in same way.

Join back seam using mattress stitch or other preferred stitch. Attach buttons to correct places on back, mine were approx 8cm in from each edge. Sew in all loose ends, and block as per instructions on ball band.

Voila!

This tank can also be worn as a halter neck by simply tying the straps behind the neck instead of fastening with buttons.

If you prefer a more varied look, you can work 2 sets of buttonholes in the straps, one at the point where they need to be to cross over and one further up the strap where they need to be for the straps to attach straight. If you use this option its advisable to sew the buttons to the inside of the tank so that you don't see the ends of the strap hanging down the back when you attach them the straight way.