An attachment tool to facilitate the attachment of one or more catheters or similar elongated instruments to a guide-wire or other elongated guide member, without requiring access to either end of said wire or member. The tool provides repeatable and reliable alignment of components to be attached, while being operated with a single hand. The catheter systems can be used for revascularization or treatment of arteries and lumens within the body, and the associated delivery of therapies therein and can include side attachable and over-the-wire components and/or low profile combination catheters to allow for flush and extraction of debris in small or tortuous anatomic pathways.