change…

plate.geo
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			h = 0.5;
			length = 2;

			Point(1) = {-length/2, -length/2, 0, h};
			Point(2) = {0, -length/2, 0, h};
			line1[] = Extrude{length/2, 0, 0}{ Point{1}; };
			line2[] = Extrude{length/2, 0, 0}{ Point{2}; };
			surface1[] = Extrude{0, length, 0}{ Line{line1[1]}; };
			surface2[] = Extrude{0, length, 0}{ Line{line2[1]}; };

			Physical Surface("outside") = {surface1[1]};
			Physical Surface("inside") = {surface2[1]};

			Transfinite Surface "*" AlternateLeft;