Well, lowneys answer below is pretty much the right answer, but the term block trigger can be used in several ways. 1*: A block trigger is a bit sticking out of the barrel that blocks the ramrod in the front: hence it's name. Nearly all guns are block triggers, except for a few that, instead of blocking the ram at the front, hold the ram back at the back of the gun. The good things of this is that it provides less friction, and that the ram can accelerate faster; both give more firepower and accuracy. The bad thing is, sears are difficult to build and can't be built on pistols. 2: A block trigger is, as opposing to a true trigger, a hinging connector on the side of the gun. See gnome master's example. 3: There is a certain type of knex gun that is typically refererred as a "noob tube", "tube and stick", "spam gun", or "knex crap", but known by the more popular name: "block trigger" . The reson why guns are called like this is, apart from their typical design, because there are way too many of these on Instructables. You can regognize a tube and stick gun by: -It's simple design; a barrel consisting out of multiple connectors stacked behind eachother on a knex rod -It's trigger, which is only a connector hinging on the edge of a knex gun -It's lack of a magazine, which means only a single bullet can be fired at a time -It's boney and simplistic design. Examples of this can be found anywhere.