the "box" is a vagina. the "nosepress" is a metaphor for oral pleasure on the said vagina. the "rail" is a penis and the "lipslide" is a metaphor for fellatio. now, the interesting part is that boxes and rails are things you can jib (which means perform various skiing stunts) on. And to top it off, lipslides and nosepresses are stunts that can be performed on those said objects, hence the clever word game and the laugh it causes. If this didn''t help you... then I guess only god can.
hahahaha i didnt need THAT in depth of an explanation, the vagina isnt really a goddamn box... and i sure as hell dont know why id stick my nose in it.
"Me and papa, build jump, in yard, back of house. I like to catch the big air. Every year I go bigger and bigger, and I go higher and higher. I could have died you know." -JF Cusson from bonus in 1242