Two Dog is the longest trail in the Croy Creek Trail System west of Hailey, and mountain bikers often call it the heart of the network. It runs about 7.4 miles from the Bullion Gulch Road side to the Croy Creek side, with a high point around 6,400 feet and a low point near 5,500 feet. Ridden from Bullion Gulch toward Croy Creek it climbs about 800 feet and descends about 1,200 feet, with a maximum grade near 14 percent. The trail is non-motorized and open to bikes, hikers, runners, equestrians and dogs. It was rebuilt by IMBA and local volunteers after the 2013 Beaver Creek Fire and reopened in 2015.

The usual starting point is on Bullion Gulch Road. From Hailey, drive west on Croy Creek Road about 4.5 miles and turn onto Bullion Gulch Road. A small parking area is on the right roughly two miles up the gulch. Some maps label the first climbing section from this end as Bull Dog, so you may see both names on signs and apps. The other end of Two Dog meets Nadya's Connector near the Rotarun area, which links to the main Croy Creek trailhead on Trailhead Road.

From Bullion Gulch the trail starts with a long, steady climb up a large, dry hillside, working through a set of switchbacks into a big drainage. It dips in and out of a small gully, then contours up the north side of the drainage and swings right around the head of the valley. One steeper turn brings you to a saddle, the high point of the ride, which looks out over a wide dry valley with rugged peaks beyond.

The descent from the saddle is the longest on the trail. It rolls across a steep, exposed sage hillside, and as you drop the view opens up into the Croy Creek valley. A few bermed turns wrap around a knoll and bring you to the Centerline junction. Stay straight here on a level stretch, then follow a mellow, winding downhill heading south. A short climb leads to the Wilson Gulch junction. Past it the trail runs downhill along a drainage, with the Wilson Gulch trail visible on the opposite hillside. The final section climbs again at Nadya's Connector to the end of the trail.

Riders describe the trail as twisty, narrow singletrack on firm, gritty dirt with flowing descents. The climbing is steady rather than steep, which makes Two Dog a good intermediate ride. A common loop starts at the Bullion Gulch Road lot, climbs to the saddle, follows Two Dog east, then drops down Wilson Gulch and returns on the Bullion Connector. Keep in mind that Bullion Connector is open to motorcycles, while Two Dog itself is not.

Almost the whole route is on open sage slopes with no tree cover, so it gets hot by midday in summer. The snow melts off early, and the Croy Creek trails are generally open from early May through mid-November. Carry plenty of water, especially if you bring a dog, and watch for other trail users on the blind corners of the descent.