The Sheet-Steel Plant Marker: A Spring Strip Instead of a Key

"The cover plate 7 of the marking card is pressed against the inturned flange 4 of the frame with such force as to maintain a substantially watertight joint between the two, and thus prevent the staining of the marking card or other injury thereto by reason of its becoming wet." "The device, moreover, does not necessitate the employment of keys or other small parts which are likely to be lost or mislaid."

**Stake.** Cut 35 cm of 25 × 3 mm mild steel flat bar, file one end to a point, and bend the top 7 cm back to about 45° in the vice, checking with the protractor. **Frame.** Cut a strip of aluminium sheet 15 mm wide and 32 cm long. Fold 4 mm of one long edge inward along its length: the bearing flange. Bend the strip round a 90 × 60 mm card into a rectangle, flange to the front, and pop-rivet the overlapping ends. Rivet a tab across the back at the top and one at the bottom, each with a 26 × 4 mm slot for the stake's end. **Backing plate.** Cut a plate 90 × 60 mm. Drill a starting hole and snip a tongue 10 mm wide and 30 mm long in its middle, then bend the tongue out into a gentle curve: the spring. **Assemble.** Put the card, a clear plastic cover and the backing plate, tongue outward, into the frame. Slide the stake's bent end through both slots so it presses the tongue flat. **Test.** Time the build and weigh the marker. Give it 30 sprays from 30 cm, wait an hour and check the card. Compare time, weight and card with a marker built to the embedded 1906 blueprint.

**Leland Willis** of Grenloch, New Jersey, assignor to the Bateman Manufacturing Company, filed US 901,137 on 29 January 1908; it is dated 13 October 1908. He also showed the ears carried on the stake and passing through slots in the frame, and the stake narrowed at the top to form shoulders that limit how far the frame slides down. **Honest limits.** Aluminium sheet and pop rivets stand in for Willis's sheet steel, and a snipped tongue for his struck-up strip. The notebook treats the strip as a straight spring arm; its sizes and presses are examples. Your spray check, weights and build times are the result.