Why did Katniss use the knife and put it in between Haymitchs hand and the table?

Watching the drunk Haymitch at breakfast, she realizes she detests him and wonders whether previous District 12 tributes lost partially because he was too much of a clown to line up decent sponsors. When Haymitch makes a joke mocking their plight, Peeta retorts sarcastically and Haymitch punches him. Katniss drives her knife into the table near his hand, and he realizes that he might actually have fighters this year. After verbally assessing their skill-sets, he agrees to stay sober enough to help them.