Answer: It depends on the throwing knives.
- Stainless Steel, Under 6″ — Cardboard boxes are fine, don’t use cork — they’ll bounce back at your eyeballs
- Stainless Steel, 6″-8″ — Thick cardboard, cork (like a dartboard), or cork w/ cardboard in front of it
- Stainless Steel, 8″-10″ — Cardboard, soft “wood” targets (read this post) or wood with cardboard over it
- Stainless Steel, 10″ and up — Soft targets or wood targets, log rounds
- 1055 Carbon Steel or better — Wood targets, log rounds
Stainless steel knives are affordable (i.e. cheap) and are great for starting out, but the tips bend when you throw against wood targets. You can try hammering them back into shape or grinding them if the tips break off, but you get what you pay for.
1055 carbon steel (used in Cold Steel throwers) is much more durable and can withstand lots of abuse. Your targets will wear out before your knives will (handle scales and paracord wrap are another story, though). I hate to sound like a commercial for Cold Steel, but their knives are just better then the other popular commercial brands. If you throw both stainless steel knives and Cold Steel knives, then you know what I mean.
And then of course, you can get stuff much better than Cold Steel from custom knife makers like Rob Crozier, Joe Darrah, Roger Mumford, or even Bo McNees (yeah, I like Bo’s lawnmower-blade knives…got a problem with that?).
More Tips: Aligning Your Blade With The Wood Grain
Worst: throwing against the grain…
An example would be having 2x4s or 2x6s aligned horizontally but throwing your knives so that they stick vertically…across or against the grain. This is really hard on your knife tips and on your target wood. Expect to see huge chips of wood flying off your target, as well as bending or breaking knife tips (particularly with stainless steel throwers).
Better: throwing with the grain…
In this case, the planks or 2x4s of your target board are aligned vertically, and when you throw your knives, they stick vertically as well. This is much easier on your knives and target board and will make them both last longer.
Best: throwing into the grain…
But the best way to prolong the life of your knives is to throw straight into the grain, head first. Examples of this would be throwing at log rounds or small 2×4 or 4×4 blocks grouped and screwed together. Some folks glue them or use create other fancy contraptions to hold them in place, but I think screws work the best and allow for easy replacement of individual blocks.
An end grain target is the best way to go to keep your throwing knives from bending and breaking by simulating a log round and allowing your blades to stick straight into the grain.
There are lots of Youtube videos showing how to make such a target, but I like this one the best…