Make a bag for your schoolbooks, gymclothes or whatever you need. By having a clear window you will easily see what's inside. You can make this any size you want, even making the window in a different shape. Make smaller ones to sort out your stuff or how about your laundry? Add pockets with or without zipper for extra stuff like keys or money. I made this one pretty basic so you will get the idea. It's supereasy to make so don't be intimidated if you're a beginner. The straps are long enough so you can wear the bag under your armpit and the bag is big enough to carry any standard sized notebooks. You can use standard cotton fabric and the bag will still be sterdy because you use 2 layers of it. I've carried mine full of librarybooks for months and it's still whole.

Stuff you will need:

*2 coordinating cotton fabrics: 50 cm each (and the usual width which usually is 140-150cm)
*a piece of soft clear plastic (like the one you use as tablecloth.) 27x15cm or depending on what size your window is.
*Basic things like sewing machine, thread, iron, scissors, ruler and some pins.

Seamallowences:
I've included seamallowences in the measurements. They don't have to be exact. I always use the edge of my foot for standard sewing and then a mark on the foot for the narrower seams. Just make sure you use the same seamallowences and you'll be fine.

I've used:
0,8cm for the straps, sides and bottom of bag
0,5cm around the top edge
0,3cm around the window and reinforcements for the straps

Finished size of the bag: 36x37cm and 52cm long straps

Step 1: Sewing the Straps Together

Start by cutting out all of your pieces:

2 pieces 37x40cm in black
2 pieces 37x40cm in white
2 straps 55x5cm in black
2 straps 55x5 cm in white
1 clear plastic piece about 15x27cm

Sew together the straps along the long edges, one white and one black right sides facing. Do the same with the other one. Turn them inside out and press the seams. If you want you can now add a narrow decorative seam along the long edges. I didn't on mine. Cut them to the exact same length if they aren't already and set aside.

TIP:
It can sometimes be a bit hard to turn the straps if they are too narrow and long. I usually use a safetypin which I pin on one edge and then lead through the tunnel. Do little at a time making sure it doesn't bundle up too much before you continue leading the safetypin through. It also helps to moisten the strap with some water. Just be careful as the fabric will be more delicate and might break more easily..

Step 2: Making the Windows

Next you want to make the windows. Take one white and one black piece of your fabric. Draw a rectangle evenly spaced on the bottom half. You can decide how big you want the window to be. If it's too big it might be more breakable. I just wanted mine to show what's inside. The measurements I used are:

8cm in from the sides and bottom. The outer rectangle is now 10x21cm, which is the size of the finished window. Measure 2cm in from that rectangle, draw around and make lines to the corners (so it looks like a picture frame)

Cut out the inner rectangle and cut up the lines to the corners. Fold them along the lines and press. Do the same with the other piece.

Step 3: Sew Sides and Bottom Together

Take both your white pieces and sew them together along the sides and bottom (right sides facing) .Leave the top open. Do the same with the black ones. Cut off a bit of the corners in the bottom. This makes the corners more pointy when you turn the bag.

Step 4: Attach Plastic to the Window

Now turn only the black bag right side out. Attach the clear plastic to the outside of the white bag's window. The plastic should be on the wrong side of the white fabric. Pin as close to the edge of the plastic (not too close to the window's edge) Put the white bag inside the black one as shown on photo.

Step 5: Sew Windows Together

This might be a little tricky, but don't give up.

Make sure the windows are aligned as you pin the fabrics together. Don't pin vertically as you would usually, but along the window instead. This gives you better control of how to fit the pieces together. Pin about 2 cm from the edge and closer to the window's edge than the pins you had in the previous step. If you don't do this you will trap the other pins and won't be able to geth them out later.

Fold the top of the bag a couple of times to make it easier to lead through the sewingmachine. Sew about 0,3cm in from the edge around the window. When you sew you won't have to remove the pins as you go although I still recommend being careful.

Remove all the pins from this and the previous step making sure you got them all.

Do not be tempted to iron the seams as the plastic will melt and ruin both your bag and iron!

Step 6: Attach Straps

Unfold the top and flatten it out. Fold the edges 2cm down to the wrong side and iron. Get your straps. Measure 2 cm in from the short edge of each strap - put a pin to mark. Measure 8cm in from the bag's sideseam - put a pin to mark. Align the strap, one at a time, so they are all the same distance from the edges. Make sure they are not twisted. Put them in between the wrong sides of the white and black fabric as shown on picture. Pin them down and when you're happy with it sew around with a 0,5cm seam.