I haven't paid a lot of attention to Lake Bernard Frank, it is kind of like the forgotten sibling of Lake Needwood. Lake Needwood is the big star with many activities, the nearby Lake Frank is smaller and there is less to do there. However, that doesn't mean it is a bad place, it is actually pretty nice and worth a trip or two.
There is a parking lot at 15211 Avery Rd, Rockville, MD and trails leading off from that. This park is run by the Montgomery County Department of Parks.
The main trail is the Lakeside Trail, it goes around the lake (but often not right at the lakeside). A portion of this trail is dirt as seen here, but a portion is paved. You can also access the Rock Creek trail from this park.
What would a lakeside trail be without a lake? Here is Lake Frank, looking towards the dam at one end. The overflow drain is visible in the distance.
A large portion of the trail is actually an old abandoned road for vehicles with access to a parking lot at the lake shore. Vehicles are no longer allowed on it.