The meaning of 1\"-8N.C.THD and 2\"x2\"x2\"STL.BLOCK

It should refer respectively to the thread type and the **specifications of the plate size

Explanation: The notation for threaded holes in the United States generally indicates the diameter of the thread, the number of threads per inch (thread pitch), the type of thread, the precision grade, the drilling depth, the tapping depth, and the direction. For example: 　　 HOLES EQUI-SPACED ON 5"DIA 　　(6 holes evenly distributed around a 5-inch circle; EQUI-SPACED means evenly spaced.) 　　DRILL 1"DIATHRO＂ 　　Drill a 1-inch through-hole (THRO＂ = THROUGH). 　　C/SINK22×6DEEP 　　Create a counterbored hole with dimensions 22×6. 　　TAP7"/8-14UNF-3BTHRO＂ 　　Tap to form unified standard fine threads, with 14 threads per inch and precision grade 3B. 　　(Note: UNF = UNITED NATIONS FINE THREAD, the American standard for fine threads.) 　　1"DRILL 1"/4-20 UNC-3 THD7"/8 DEEP 4HOLES NOT BREAK THRO 　　Drill a 1-inch hole, tap to form 1"/4 American coarse threads, with 20 threads per inch; the tapping depth is 7"/8. The 4 holes should not be drilled all the way through. (UNC = UNITED NATIONS COARSE THREAD, the American standard for coarse threads.) 　　1"-14NS-2THRO 　　Tap to form American standard special thread M1", with 14 threads per inch and precision grade 2. 　　(Note: NS = NATIONAL SPECIAL THREAD, an American standard for special threads.) 　　Therefore, the owner’s “1"-8N.C.THD” should refer to “Tap to form American standard ordinary thread M1", with 8 threads per inch and precision grade 1.” The second piece of information you provided is inaccurate; it can only be determined that STL refers to stainless steel material. Could it be referring to a nut or gasket for flanges?