You may need to trim bamboo Roman shades that are too long or too wide for the window where you wish to install them. Follow these procedures to effectively trim your bamboo Roman shades and the headrail to fit them to your window.
Step 1 - Decide Where to Trim
Measure the width of your window to decide where to trim the width of the shade. Decide on an inside or outside mount relative to the window frame. Note that bamboo shades effectively block more light when mounted inside the window frame than outside. Measure the shade headrail and mark the trim line with a pencil.
Step 2 - Trim the Width
Set up the power table saw in a safe outdoor or basement location. Roll up the bamboo shade as tightly as possible. Secure it to its wooden headrail in three places along its length with masking tape. Lay the shade plus its wooden headrail (see Step 3 for a metal headrail) on the flat plane of the table, and ask an assistant to hold the far end away from the saw blade. Both of you will guide the headrail and shade slowly through the saw for a clean cut.
Turn off the power table saw. Sand the headrail edge with coarse, then fine-grained sandpaper. Add new lifting cords up the back of the shade as needed to balance the lifting function.
Step 3 - Trim a Metal Headrail
You can cut a metal headrail down to size with a hacksaw. Mark the cut line on the headrail with a permanent marker, then lightly score the cut line. Move the hacksaw with firm, smooth strokes, pressing firmly downward until you cut all the way through the metal. Shave off any jagged metal with a file or with the power grinder.
Step 4 - Measure the Desired Length
To decide where to trim the length, fully roll out the bamboo shade. Measure your desired endpoint and draw a pencil line. Lay masking tape across the shade just above the line, and add four inches to make your cut line to avoid damaging or unravelling the bamboo slats that will become the bottom of the shade. Put a second row of masking tape just above your cutting line.
Step 5 - Trim the Length
With the wire snips, cut carefully across the full width of the bamboo shade, staying below the lower masking tape line. Remove the tape and slide out the bamboo slats from the binding strings up to the new edge. Unwind the binding strings and knot each of them at the new endpoint. Cover the new bottom with a thin layer of masking tape.
Step 6 - Replace the Shade Base and Hang
Pull the slotted base off the old bamboo slats, and slide the new bottom of the shade into it. Hang the shade in its new location, check the cords and test its operation.