Planishing can change the shape of the piece you are working on in ways you may not have wanted it to.
In this video I am working on some greaves that have altered shape a little during planishing. Often, not always, the error can lie not in the edge but a little way back from there. The same can be found on any piece of armour - not just greaves.
![](https://s2.save4k.ru/pic/W_lCS-14Rs4/maxresdefault.jpg)