Could you help me get my chest measurement with this tape measure?
A scroll of shaku. So, a scroll is all rolled up, right? And a shaku is an older form of Japanese measurement. If you roll up a measuring thing into a scroll-like container... what does it become? A tape measure!
The reading for 巻 is the 巻く reading, pushed into the kanji. The 尺 reading is the normal reading of 尺. Careful of the rendaku.