+catch_cr = catch_knob_dia/2 + catch_stem_beside_gap;
+catch_strap_width = sm_main_width;
+
+cpp0 = [0,0];
+cpp1 = cpp0 + [0,1] * catch_pin_height;
+cpp2 = cpp0 + [1,0] * (rivet_entry_width - catch_pin_gap);
+cpp3 = cpp2 + [0,-1] * catch_stem_end_h;
+cpp4 = cpp2 + [0,-1] * catch_stem_end_h;
+cpp5 = [ cpp0[0] - catch_stem_len,
+ cpp0[1] - (catch_stem_h + catch_cr) ];
+cppB = [ 0.5*(cpp1 + cpp2)[0],
+ cpp1[1] - catch_pin_height - catch_knob_above_gap -
+ 0.5 * catch_knob_dia ];
+cpp7 = cppB + [-1,-1] * catch_knob_dia/2
+ + [ catch_stem_beside_gap, -catch_stem_below_gap ]
+ + [ 0, -catch_pin_height ]
+ + [-1,1] * catch_cr;
+cpp6 = [ cpp5[0], cpp7[1] ];
+cpp8 = [ cpp7[0] + catch_cr*2,
+ cpp0[0] - catch_cr ];
+cppC = cpp8 + [1,1] * catch_cr;
+cppA = [ cpp5[0] - catch_cr*2, cpp0[1] ];
+cppD = cppC + [0,-1] * catch_strap_width;
+cppE = [ cppA[0], cppD[1] ];
+