Jackknife was born in Ponyville, but he moved out to Mount Hoof for the slower pace and great views. Although he maintains a small cottage on the mountain, his talent causes him to do quite a lot of travelling. Jackknife helps out at big events around Equestria, travels to farms to help the various fruit harvests, and generally tends to show up wherever a lot of hooves are needed.
Jackknife's main talent is... not really having a specific talent. As his cutie mark suggests, Jackknife's skills are varied; he can build, harvest, paint, sew, and even arrange flowers... he'll just never do them as well as a pony who actually has a talent in the area.
He's never come across something he's really bad at (yet) but he'll never be an innovator, either. Jackknife is alright with that; he realized long ago, that sometimes it's better to just be a friendly helping hoof when somepony needs it.
Jackknife would be happy to help out with any job you have that needs an extra set of hooves. He's currently located on Mount Hoof as I get used to this new format of RP, but he will be making frequent trips to Ponyville, Canterlot, etc. in the future.
If you'd like Jackknife to be on hand when you start a new journey/project, send me a DM and I'll try to get him in place for ya.