L1 – Extensions and Lunges
L2 – Hamstrings
L3 – Leg Press Machines
L4 – Squats
L5 – Straight-leg Calf
L6 – Bent-leg Calf
L7 – High-rep Calf

Single Exercise Videos:

Leg Extension Machine (L11)
      with rear weight stack (L11A)
      old-style, chain driven machine (L11B)
Dumbbell Returning Lunge (L12)
Dumbbell Walking Lunge (L13)

Seated Hamstring Curl (L21)
Lying Hamstring Curl (L22)
— another machine design (L22A)
Barbell Stiff Leg Deadlift (L23)
Single-leg Bench Hips Raise (L24)
Swiss Ball Hips Raise (L25)
Hamstrings on Leg Press Machine (L26)

Cradle Leg Press Machine (L31)
Sled Leg Press Machine (L32)
Seat-move Leg Press Machine (L33)

Back Squat (L41)
Smith Machine Squat (L42)
Sumo Squat (L43)
Goblet Squat (L45)
— bodyweight only (L45A)

Calf on Leg Press Machine (L51)
Standing Calf Dumbbell Raise (L52)
Rotary Calf Machine (L53)
Standing Calf Raise Machine (L54)

Seated Calf Raise Machine (L61)
Seated Calf Dumbbells Raise (L62)
Calf on Leg Extension Machine (L63)

Toe Taps + Heel Raises (L71)

Multi-Exercise Videos:

Leg Extensions (L11) and Lying Hamstring Curl (L22)
Three additional types of leg press/squat machine
Six key upper leg (L1-L4) exercises in one workout