Re-using old fabric
Some time ago (probably 7-8 years) I visited Glasgow, and of course that happened what has to happen in Scotland - I brought some tartan farbric home with me.
This was used to make a skirt that has been used since then, although not as much as expected for some strange reason.

When trying it on some time ago it was clear that it was getting to small (how did that happen?) and the question was - what to do with it? Give it away to charity or re-do it into something else - since I still had some non-used fabric left?
I decided to try the second solution, and went searching for a jacket-pattern - since nice, "homemade", jackets are scarce in my wardrobe. This might seem strange for someone who spends so much time in the sewing room...
The first thing to do after that was to open up the skirt.

 When this was done it was time to check whether the amount of fabric was enough for what I 
planned...

 The first pattern I tried turned out to need more fabric than available, so I had to go for a shorter jacket than planned - luckily I had an old pattern lying around that was perfect.

Surprisingly enough it was possible to match not just all the seems around the body but also the arms - this is how the jacket looks being stitched together for the first fitting.