Here's a video of a dude doing knives hits but with herb, same technique just place concentrate instead, also make sure the knife stays flat as you don't want oil dripping while it's still melting. I love knife hits, but if you're going to dab, buy a nail attachment for your bong,the range from 15$ for glass to up to 60$ for titanium or quarts some even more expensive, the higher end ones like quartz which I prefer, have a cleaner smoother better tasting hit. But a cheap glass one is good enough to last you couple months