Row 1: 1tr in 3rd ch from the hook, 1tr in each ch to last ch (50tr), turn
Row 2: sl st in every tr across (50 sl st)
There are two ways to attach your crochet strip to the board or frame.
A temporary solution will be to simply tape the ends to the back of the board to the edges. This will usually hold for a while if you apply enough tape, but this is still only a quick-fix.
Temporary tape solution.
A more effective way would be to use a hot glue gun to attach the ends of the strip to either side of the board. Once it's dried and set, it should hold relatively well.
Secured using a hot glue gun.
You can then hang it on your wall, and remove and replace at will.
I used an 8ply acrylic yarn for this project, but you'll probably want to something stiffer, because it will stretch.
The length of your strip will depend on the size of your board. The one I worked with was 29cm x 29cm:
Magnetic dry-erase board from Officeworks
The length of your chain is determined by measuring the number of stitches you need, plus an additional two chain stitches to compensate for the height of the next row.
For example: This project is 50 stitches in length. I added two extra chain stitches to my initial chain, because a treble crochet is three times the height of a chain stitch. Without the two extra stitches, the beginning of the second row will curl in on itself because it is not the same height.