[BigJim]

A couple of things I can think of off hand, put as large a piece of wood in the hole as you can, then screw the bolt back in, it might help if you glued the wood in and let it dry first. Another thing you can do to tighten the screw up is cut a strip of #12 or #10 single strand electrical wire with the insulation left on, insert the wire into the hole as deep as it will go and then reinstall the bolt, the wire will force the screw to make new threads into the wood as well as the wire.

 

[Serious Roofer]

the above is a option, woodglue mixed with sawdust works alright, but try using a longer bolt ? so it has something to grab onto? without going through the wall of course.

 

[Ron6519]

You can also drill a hole and glue in a dowel. Size would depend on the fastener size used before. Let the glue dry over night and drill a pilot hole into the dowel.
Don't use old glue, it looses fastening power.

 

[user1007]

the above is a option, woodglue mixed with sawdust works alright, but try using a longer bolt ? so it has something to grab onto? without going through the wall of course.

:thumbsup:A longer lag bolt seems prudent whatever method you pick here. But...

What size lag bolt is this by the way, diameter wise? I hope it is going relatively straight into near the center of a stud and has not fractured away the edge of one? All the dowels, wood glue, and wood patch materials we can suggest will not fix the latter situation. Nor will a longer lag bolt.

Try the longer lag bolt first.