「Person kneeling, on all fours」who is「in use」depicting to PASS THROUGH, a PATH BETWEEN WALLS, noting the glyph meaning「wall」(壁) uses elements of「anal penetration in soil」passing between walls of muscle tissue. Old version added the「woody, wood」element (桶), the use of a receptacle or an open cavity to temporarily hold some contents, such as untreated excreta transported without water (e.g.,「shimogoe」via containers or buckets). Ask yourself, how often did a roadway pass between soil walls thousands of years ago? there wasn't a need for overpass-underpass construction even in the highest-traffic areas, and soil walls have a tendency to erode rather quickly during rainstorms albeit reinforced with wood.
A「container for holding contents a brief time」as a BUCKET used for collecting feces, among other functions (「protruding buttocks, in use.」…think about it).
From time immemorial before the beginning, humans have collected feces and used it as fertilizer. Still today, researchers are working on finding solutions for problems facing humanity. It is not only feces that are an excellent fertilizer. Urine works, too! "Innovative system turns human waste into sustainable fertilizer: Stanford researchers have developed a prototype that harnesses urine to generate valuable fertilizer, offering solutions for sanitation and energy in resource-limited regions."
[ https://news.stanford.edu/stories/2025/08/prototype-urine-human-waste-fertilizer-sustainable-energy-research/ 2025-08-21 ]
「Person kneeling on all fours」after「shuttling」past a「gateway」(now closed, being 'in use' of course) and「using」the services within, perhaps by shuttling around to the various groups.
SHUTTLE as in regularly moving back and forth over an established, short route, one well-known and often used, to mean PASSING THROUGH but only remaining for a brief time in any one place.
Alternatively yet unlikely, some suggest the「shuttle」of a loom「in use」to pass the weft threads through the warp threads. The shuttle continually was used to PASS THROUGH from one side of a loom to the other, guided by the warp threads above the「spread legs」of a person operating the loom and treading on the treadles (not much to do with buckets, unfortunately).

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: path screened by walls on both sides; variant of 桶 , bucket; (classifier) cubic dry measure (5 pecks 五斗, approx half-liter)
Japanese EDRDG: road with walls on both sides
Unihan extended: path; river in Ningbo; Ningbo