There is an arm at the left side of the bottom roller. This arm can be bent or broken (like mine). Either get a new arm if needed or go to a dismantler and buy a used one and replace it. It is held in place with a single bolt (12mm I think).
Friction between your shoes and the ground is the force that keeps your feet from sliding as you walk. The rough texture of your shoe sole and the ground surface creates resistance against sliding motion.
what stops food from sliding up from your stomach when your standing your head
Keel
Friction.
The force that keeps a box from sliding down an angled conveyor belt that slopes upward is friction. Friction acts in the opposite direction of the box's movement, preventing it from sliding down the slope.
The window keeps sliding down because the mechanism that holds it in place is not working properly.
traction
yes
Static friction keeps an object from moving when a force is applied. It is the force that must be overcome to initiate movement of an object. Sliding friction occurs once the object is in motion.
Friction is the force that keeps you from sliding on an icy sidewalk. When you walk, the friction between the soles of your shoes and the ice surface prevents you from slipping.
end caps and stops
Friction is the force that keeps you from sliding off a sled when it starts moving. When you sit on a sled, the friction between the sled and your clothing provides the necessary grip to keep you in place as the sled accelerates.