DWR Custom Woodworking offers 2 different ladder as pictured.  The Quilt Ladder has parallel side rails and the Apple Ladder has tapered side rails. Assembly is the same on both ladders,  a tapered peg is inserted into a holed drilled in the tenon of the rung.

                                                                                                 
                                                                                                                 9290 Quilt Ladder

                9590 Apple Ladder