The ascent of Bob's Hill from the Catoctin State Park Manor Parking Area (immediately adjacent to US Highway 15 south of Thurmont; $3 per vehicle for Maryland residents, almost always on the honor system) is indeed a good strenuous walk. This trail offers 1000 feet of vertical elevation change in a mile and a half: one of the best places for serious hill walking training in the state east of the Allegheny mountains. The trail is wide but rocky. It passes through lovely Mountain Laurel undergrowth in several areas; and in one of those areas, about two thirds of the way to the summit, one can find abundant pink lady slippers blooming in late spring right alongside the footpath.
The trail has several steep sections, the steepest of which is immediately below the "summit" marker (where the two trails to the two lookout points split off). The marker post is actually set at an elevation of just under 1700 feet--the high point of Bob's Hill is a rock pile nearby--a short bushwhack.
From the Catoctin State Park Manor Parking area trailhead (located directly across from the playground area) the trail is marked with triangular yellow reflectors. This is just a short connecting trail, a few hundred yards in length. It intersects with the blue blazed Catoctin Trail after a short steep climb; and from there the trail ascending Bob's Hill is marked by both the blue paint blazes maintained by the Potomac Appalacian Trail Club and the triangular yellow reflectors that appear to be maintained by the State Park.
There is an alternative free parking area a short distance to the south of the Manor Parking area, and across the busy US15 highway. This is at the historic ruins of the Catoctin Furnace (remains of a large iron smelting mill). This parking area is accessable from Rt. 806, the frontage road that parallels Hwy 15. A trailhead from there (no sign identifies it; it starts from the grassy area just up the hill and to the right of a small handicapped parking lot and a separate trail that leads to one of the ruins) leads over a dedicated foot bridge that safely crosses over the busy divided highway US 15. From there the trail enters the Manor Parking Area picnic area. Stay to the left among the picnic sites between Little Hunting Creek and the parking lot. Follow the creek upstream and you will quickly intersect the well-marked blue-blazed Catoctin Trail where the picnic sites end. Follow the trail right (do not cross Little Hunting Creek) and ascend via a winding route for a few hundred yards to the intersection with the yellow-reflector-marked spur trail that comes up from the Manor Parking lot trailhead mentioned earlier; turn left at this intersection and continue on to the Bob's Hill summit. This extension adds another 150 to 200 feet of elevation change and perhaps another 0.4 miles of distance to the walk.