Screws, also known as anchors, are hazards and helpers in World of Goo. Once a screw touches a wall or floor, it will stick to that surface permanently. Screws can have Goo legs attached to them, but they cannot fly away with Balloon Goo or fall over in the event of a collapsing structure. In Upper Shaft, using the screw is not necessary for the OCD, but is highly recommended. In Blustery Day, a screw is what prevents the player from sending their Water Goo structure flying away. In Horizontal Transportation Innovation Committee, a screw causes the most mistakes because of structure over-balancing issues. Surprisingly, screws can be collected into pipes. Screws can be visible at times, but sometimes they are invisible so they cannot be seen. One thing that has been noted is that if one attaches more than seven legs to the screw in Upper Shaft, it always causes uncontrollable vibrations.