easy instructable,built on nothing but a IKEA blue bag and some scrap parts.
convert a IKEA blue bag into a rather small backpack
(30cm * 10cm * 40cm) or (12'' * 8'' * 16'')

Step 1: Materials and Preparation

Tools needed :

1)a drill with thin drill bits for metal
2)a hand-saw
Materials needed :

1) IKEA blue bag
2)needle and thread (preferably a strong one,
    i got mine from a leatherworking shop)
3)hard rubber for the back (i found mine at the garbage, it's used for repairing shoes)

thats all.

Preparation:

1) cut the blue bag as instructed on the fouth image.
     (cut the perimeter of the entire piece, plus the long handle on one side,
      plus the entire long handle on the other side)
2) drill holes on the hard rubber, and tie the parts together
     as shown on the first and second image.
     (i used fishing line here for the joints to be more flexible and durable)
3) the plastic on top shown on the third image is the bumper from an old car.if you have
     something similar use it,else skip this part.

Step 2: Knitting,knitting,knitting..

now comes the knitting part.

this wont be hard but is gonna take a while.
Firstly place your hard back on the piece of the blue bag that you cut on the central number 1 part.
Then fold the lower number 4 part over and sew it over the hard back on the upper number 4 part
Then fold the left number 4 part over the right number 3 part and sew them together.
Then fold the righ number 1 part over the left number 1 part and sew them together.

sew both long handles on the four corners of the number 1 part.

now trace the edges of the front of your backpack on the remainder IKEA blue bag and cut it.

sew the piece that you just cut on the lower edge of the back

sew a zipper on the 3 remaining edges.

that should be all.