Abstract: A ruler having two slidable parts includes a ruler body, which is formed in rectangular shaped, the ruler body having a first recess extending longitudinally on its top surface and a second recess extending longitudinally on its side surface, a hand stand having a wheel, which is coupled with the second recess of the ruler body, and a wrist stand, the wrist stand having a wrist rest portion, a support portion for supporting the wrist rest portion, a joint connecting the wrist rest portion and the support portion, and ground portions attached to the support portion, wherein the ground portions are grounded to the bottom of the first recess.

Abstract: A heat transfer fin (1) includes a plurality of heat-transfer-tube insertion holes (10) aligned in a single stage, a downstream cut portion (3) formed so as to be recessed toward an upstream side of a gas flow passage of combustion exhaust gas, a downstream flange (13) formed on a peripheral edge of the downstream cut portion (3) so as to protrude from one surface of the heat transfer fin (1), and a plurality of first protruding pieces (4a) (4b) (4c) formed between the heat-transfer-tube insertion hole (10) and the downstream flange (13) so as to protrude alternately from both surfaces of the heat transfer fin (1).

Abstract: A heat transfer fin (1) includes a plurality of heat-transfer-tube insertion holes (10) aligned in a single stage, a downstream cut portion (3) formed so as to be recessed toward an upstream side of a gas flow passage of combustion exhaust gas, a downstream flange (13) formed on a peripheral edge of the downstream cut portion (3) so as to protrude from one surface of the heat transfer fin (1), and a plurality of first protruding pieces (4a) (4b) (4c) formed between the heat-transfer-tube insertion hole (10) and the downstream flange (13) so as to protrude alternately from both surfaces of the heat transfer fin (1).