I'll try my best to explain this in text format -

this came out much longer than i expected, but i really tried to give as thorough of an explanation as i possibly could + i tried my best to help you visualize it the way i do.

quick note: the basement skip took me roughly an hour to get for the first time, but the more you do it, the better you're able to visualize it yourself. i can do it >60% of the time now (except when it actually matters) so it's really just practice once you get the method down.

quicker note: the upstairs skip utilizes the exact same method, just mirrored on the other side of JRB

- refer to this run alongside the explanation to see what im talking about

it's easier to break the trick down into 3 parts:

part 1: the first two jumps to set up your position - https://imgur.com/2fTgPQw refer to this image

• if you watch the run, i jump up the invisible wall twice in order to set myself up for part 2 where i will check if i have clipped through correctly or not. in the image, it shows roughly the 2D plane that you'll be jumping on. there are two thick lines labeled 1 & 2 - think of them like rungs of a ladder that you need to climb, the first jump will land on 1 and the second will land on 2. your goal is to be against the front wall and reach roughly around the height of 2 using those two jumps. they do not need to be max height, but as long as you get a noticeable amount of height per jump, then you should be okay to move on to part 2.

troubleshooting with part 1:

• you want to use the right edge of the front wall (the brick wall you are facing that is visible) as your guide, and you want to try and stay on that line, as if you go too far to the right, you will clip through and will have to try again. you also do not want to be too far back as you could clip through the back end of the wall as well.

part 2: once you have successfully made it onto the 2nd rung of the ladder from the image above, and you are not stuck or too far to the right, then your next step will be to jump once to see if you have gotten the proper clip needed to jump onto the wall or not. the method i use is to align myself straight against the right edge of the brick wall, and jumping once.

this jump can yield one of three options:

correct cue: you are able to do a full, max height jump when standing on the 2nd rung, which goes all the way up and then lands back on the 2nd rung; DO NOT MOVE in any direction after this jump has been completed, as you will need to jump straight onto the wall (part 3). your character may move slightly as if jumping into a curved surface, but this is exactly what you're looking for. proceed to part 3.

reposition cue: if your jump does not get max height and hits the ceiling prematurely, but still comes back down to land on the second rung, then this signifies that you are not far enough to the right to properly test for the clip. as long as you aren't stuck, you can do a very (VERY) light tap to the right, and jump again. if the same thing happens, then repeat until you get either the correct or the incorrect cue.

incorrect cue: this could take several forms and will always mean you must retry- a. your jump gets you stuck in the ceiling; i think this signifies that you were either too far right, or you were slightly in front of the front wall, not completely sure b. you fall down to the ground/out of the map; this means that you ran off of the second rung in a direction before doing the test jump c. anything else that gets you stuck/does not allow you to jump again; you screwed somethin up, no biggie just try again

part 3: this is where you bring home the bacon. once you have cleared the test jump and are able to do a full jump, you want to jump up and land on top of the front brick wall. this is a little bit of a tight jump since it's onto a thin edge, but trust your instincts. once you land this first jump, you will then want to jump onto the edge of the little brick hole in the wall to your right. these jumps are fairly straightforward since there isn't anything invisible to navigate around, it just comes down to platforming skills.

this is it, the final jump. you will be jumping from the little brick edge, all the way down to the basement loading zone which is behind the doors. this is a fairly simple jump, as long as you JUMP FIRST, and then input W + SPRINT IMMEDIATELY AFTER. far too many times have i seen either myself or someone else just run off the little brick edge because they tried to be a big gamer - just play it safe. you MUST be sprinting to make this jump however, and by then, you're well on your way to meeting the big man.

ggs

Here is another explanation video with keyboard inputs on screen: