In the scene Vince and Turtle are at a local gun shop looking for a gun to protect themselves from a burglar that broke in their house the night before. They were disappointed to find out that there is 10 day waiting period. As they needed something to protect themselves now.
At that point the guy behind the counter asks "Do you like knives?" and pulls out the Tigershark Elite.
Update: We got a clip of the scene. Check it out below.