It is not necessary to write off old equipment or household items that cannot fulfill their direct functions. For example, old bike, on which you wind an incredible number of kilometers, can find a second life as a stool.
First of all, cut out the back triangle, as shown in the photo.
To give stability to the stool, it is necessary to provide a larger base width than the bike initially gives. To do this, you need a wooden block in which holes are drilled. Metal tubes of a bicycle frame are fixed in them.
It remains to make a seat. It can be made from a suitable piece of wood. Since, nevertheless, the bicycle is the cornerstone of the stool, by paying tribute to it, the seat can be made in the same shape as the native bicycle. Fix it and enjoy the results of your labor.