Half Pipes are structures found throughout the Metroid Prime series. They are formed of two concave ramps with a flat middle section and vary in height. Samus can use the Boost Ball on these Half Pipes to climb up the walls of them.
Half Pipes are the product of various natural and artificial occurrences; examples include the large Half Pipe structure in Phendrana Canyon which is a product of ice frozen in a smooth pattern and the Half Pipe in Command Courtyard which was created by a Space Pirate mining drill.
Half Pipe structures work with the Boost Ball much like Wall Jump Surfaces with the Screw Attack or Spider Ball Tracks with the Spider Ball; Half Pipes are only useful once Samus has obtained the Boost Ball. To use them, Samus must boost back and forth in her Morph Ball, using gravity in conjunction with kinetic energy produced by the Boost Ball to gain momentum and reach higher places. Expansions are often placed near or above these surfaces.
Metroid Prime 2: Echoes