I am working on this free download pattern, which doesn't seem to be available for download anymore, but I found this picture of the quilt offered as a kit:
http://www.craftycornerquiltandsewingshoppe.com/shop/Kits---Name-of-quilt-opens-for-more-information/p/Two-Bluebirds-Quilt-Kit-x4118198.htm
The triangles are sewn together in alternating directions to make the two columns. I pinned the straight edges of the triangle pairs together, matching the ends as I would normally do when sewing two pieces of fabric together. As I sewed the pairs of triangles together into larger groups, I noticed that the column was slanting. I wondered how I could sew the straight piece of fabric representing the trunk, to this slanting column. I decided to trim the edges of the first column to get a straight edge (even though the quilt measurements given indicated they hadn't trimmed theirs).
The result of the trimming was that the triangles no longer looked like the photo of the quilt. In the photo, the triangles are skewed, which gives movement and interest. What I ended up with was each pair of triangles forming a rectangle with the bottom edge on the true horizontal. It looks flat and static this way.
Can anyone explain why the column is slanting, and if I should somehow be sewing the triangles together differently to avoid this?
Below is a photo of the first, sewn and trimmed column, and below that is a photo of the two columns before sewing (where the triangles do look skewed, as in the quilt photo). Unfortunately, I didn't take a photo of the first column slanting.