detailed, fine, closely woven
縝 centers on fine, dense detail: something closely woven, finely detailed, or meticulously made. The idea of tight, careful construction connects the given meanings.
縝 combines 糸 (thread) with 真, which likely contributes the sound and the idea of something genuine or dense, suggesting finely detailed weaving.
The left side is thread 糸, and the right side is 真 (truth/reality). Picture a weaver checking every thread for truth, making the fabric closely woven and detailed.
For シン, imagine a thin, fine thread being woven: thin -> シン, and the thread creates a closely woven, detailed fabric.