+hex22 = hex21 + hinge_x_gap;
+hex23 = hex22 + hingescrew_portion_len
+ - hingescrew_nut_thick; // bodge, need to divvy this up more sensibly
+hex24 = hex20 + hingescrew_shaft_len + hinge_x_postscrew_gap;
+echo(hex20, hex21, hex22, hex23, hex24);
+echo(hingescrew_portion_len);
+
+// catch
+
+cppJ = [ epp4[0] + catch_thickness, lpp10[1] ];
+cppA = cppJ + [lid_gap_x, -lid_gap_z];
+cppB = [ epp0[0], cppA[1] ];
+cppP = [ epp4[0], cppJ[1] ];
+
+cppS = cppJ + [0,-1] * catch_len;
+cppD = [ cppA[0], cppS[1] + catch_slop ];
+cppC = [ cppB[0], cppD[1] ];
+cppT = cppS + [1,0] * catch_depth;
+cppU = cppT + [0,-1] * catch_height;
+cppV = [ cppS[0], cppU[1] - catch_depth ];
+
+cppR = 0.5*(cppP + cppJ);
+
+cp_rQ = 0.5 * (cppJ[0] - cppP[0]);
+cppQ = [ cppR[0],
+ cppV[1] - (catch_finger_height - cp_rQ) ];
+cppF = [ cppV[0] + catch_finger_depth, cppC[1] ];