Noclipping is the action of travelling quickly enough to pass through a solid object. This is considered the main method of entering and exiting many of the levels in the Backrooms. While noclipping is a fairly supernatural process, it draws similarities with quantum tunneling. A human being does not possess enough energy to penetrate the barrier between the Frontrooms and the Backrooms. However, in rare areas where the barrier is thin enough, a human may be able to "borrow" the energy of a noclip channel, passing through the barrier without breaking it.
Noclip channels are mysterious forces that can be described similarly to wind currents. They have an impossible, potentially infinite amount of energy, and act as a gateway between locations. They pull in a single direction, in a vacuum, with speeds that quickly grow exponentially. Their force extends beyond the barrier a small amount, meaning that a human with enough energy going into a noclip channel can be "picked up" by it and gain enough energy to quantum tunnel. This process usually takes around four seconds. They can be anywhere, functioning as the roads of the Backrooms. Notably, there is only a single confirmed noclip channel leading into the Frontrooms, but thousands leading out. Despite their convenience, they are not entirely safe.
First of all, not all noclip channels end in other levels. Some end in the middle of the Void, having a small chance of stranding the wanderer there. Noclipping, if unsuccessful, can lead to serious bodily harm from the high velocities it requires. Worse, if noclipping is only partially successful, it can lead to absorption where a wanderer may end up inside of a wall, instantly dying. Some advanced entities are capable of opening up these channels and using them as traps, or purposely absorbing themselves into walls to lie in wait.
Successfully noclipping is most probable in areas where the barriers are thin, such as abandoned office buildings, maintenance tunnels, or other isolated locations. While running into an unusual-looking wall in an abandoned office building has a chance of successfully performing a noclip, performing the same action inside of a familiar and warm apartment building has a near-zero chance. Anything unusual or disconcerting is likely where the barriers are thinnest.
Finally, time inside of the Backrooms functions differently in relation to the Frontrooms. Time seems to be a factor in what noclip channels exist and therefore what levels are noclipped into (ie. those born before fluorescent lighting are much more likely to noclip into a non-0 level). Mirroring that, however, the location of a wanderer in the Frontrooms at time of noclipping appears to be correlated to the time that they arrive in the Backrooms. It is thought that this is not a direct correlation, and that there is a confounding factor. This phenomenon is known as temporal displacement.
How Do I Noclip?
To noclip, one needs to be travelling quickly enough to pass through any solid object like a wall without breaking it. If this is performed successfully, one will have noclipped. However, as mentioned previously, it is quite easy to incorrectly perform this, causing injury, death, or eternal torment. It is difficult to predict with any level of certainty, and all of it is based off of luck.