Powder your exposed skin with baby powder. This fills the pores and prevents itching when you are exposed to fiberglass insulation. Don your work gloves.
Cut the insulation off of the portion of the ducting that will be removed for rerouting using the scissors. Trim back at least 6 inches from the line where you will cut the duct to attach the new ducting.
Remove all segments of duct between the points where you will detach or cut the existing ducts in order to reroute them. Unscrew circular ducting. Pry off the cleats for rectangular ducts with pliers and unroll the fold-over connections. Wiggle free the unwanted sections.
Measure the new attachment points for the re-routed cuts using the tape measure. Mark your cuts for the new attachment points using the metal scribe. Cut the duct with the tin snips along the line you scribed.
Connect the new ducting. Attach rectangular ducts using a fitting if you have had to cut the existing duct. Attach circular ducts by fitting the crimped ends into the un-crimped ends. Crimp ends, using the duct crimpers, where cutting has left two un-crimped ends joining together. Re-fold the edges of the rectangular joints with your pliers. Place cleats every few inches along the fold and tighten them onto the folds using the pliers. Drill circular joints at four points along each joint and screw the joints together with the sheet metal screws.
Screw a wood screw through one end of each galvanized hanging strap into the ceiling joist directly above the edge of the new ducting. Fold the strap around the ducting and hold the free end of the strap against the joist where you want to connect it to suspend the duct level. Check level for the duct. Screw in the other end of the strap. Repeat as necessary to ensure a strap at least every 3 feet along the duct.
Tape the joints with at least four wraps of duct tape on each joint. Re-wrap all exposed ducting with insulation, taping together the edges where insulation meets insulation.