Bend J-Channel and Window Head Flashing on a Tapco Brake

October 31, 2022



How to bend common window profiles on a Tapco brake  

J-channel is used at the sides of windows, and an L-shaped head flashing is used at the top. Here's how to form them in the field.

Step 1: cut the coil stock to width

J-channel uses 3-1/2 inches of coil stock. The coil stick cutter slices a line 1-1/2 inches past the clamp, so set the coil stock with 5 inches protruding past the clamp and cut.

Step 2: hem the edge

Hemming the edge reduces the chances of slicing your hands on the sharp metal and it also produces a stiffer, more attractive edge.

  • Insert the coil stock 1/2 inch into the clamp and clamp.
  • Bend as far as the brake will allow, using both handles to ensure a consistent bend.
  • Reclamp the brake and drop the edge into the front of the brake using the hinge to continue the fold creating the hem. 

Step 3: Complete the J-channel

  • Reinsert the workpiece into the clamp 3/4-inch with the finish side down.
  • Bend 90 degrees and release the clamp.
  • Slide the coil stock out an additional 3/4-inch
  • Bend 90 degrees again to complete the j-channel

Bend an L-shaped window head flashing

  • Hem the edge
  • Insert the hem into the brake, finish side down, and clamp the brake at the edge of the hem.
  • Bend 90 degrees and release the clamp.
  • Slide the long edge in with the finish side up. Leave enough flashing outside the clamp to cover the window head.
  • Bend 90 degrees for a complete window head flashing.


—This video is from Tapco Tools, one of ProTradeCraft's advertisers. Serving professional siding applicators since 1961, Tapco brakes and accessories bring measuring, mobility, decorative designs, and strengthening ribs to fascia, window trims, frieze boards, porch posts, and beams. See all of Tapco's content here.