I use an old layed foam archery target.
I throw 6 x 14 inch 600 gram home made knives and 3 cold steel perfect balance = 9 knives in total.
The knives rip up the foam. If they go in parallel to the foam, that's OK.
It's when they turn 90 degrees, and cut the foam layers that damage is done.
My old archery target lasted about 1 month, throwing every day, about 50-60 throws.
I turned it round, and put a cover of pallet wood over the foam area,
hanging it off the wood frame of the foam butt.
Although the knives go throughthe pallet wood - about 1/2" -3/4" they don't cut up
the foam so much, and the pallet wood is easy to replace (and free!).
This way I have the knives stick and stay, although the wood does split etc.
The foam target is against a wall, so no movement on impact.
The advantage of the foam is that the target can be dismantled,
and the foam layers re-stacked, and them recompressed.
The wood & foam combination last as long as the wood is usable,
but around 2 months i.e. 50 knives per day x 5 days per week for 7 - 8 weeks.
Then replace the wood (in my case).
About 750 - 1,000 throws.
