Devices and methods for achieving directed placement of guidewires or other flexible rails over which other catheters or other devices may be introduced to a targeted location. A guidewire directing device includes a lumen extending between a proximal end and a distal peripheral opening for directing a guidewire laterally from the device, and may have a deflecting member with a predetermined deflection angle in the lumen adjacent the peripheral opening. A snaring device is also provided that includes one or more lumens through which a snare or other grasping member is directed for releasably capturing or coupling to a guidewire. The snaring and target guidewire devices may include cooperating end effectors for releasably coupling or securing the devices together. The devices may be used for directing, snaring and/or manipulating one or more guidewires between two blood vessels connected by an interstitial channel, for example, to "floss" a guidewire through the coronary arterial and venous systems between two percutaneous entry sites and/or to bypass a lesion in a vessel using proximal and distal interstitial channels communicating with an adjacent vessel.