Toe lock
A niche add-on hook or block at the front of the foot that catches the shoe near the toe box or in front of the ankle. It gives more vertical hold than a normal pedal riser, especially during jumps and aerial tricks.
Do not confuse this with a toe lift or toe riser built into the pedal. A riser gives your shoe a shaped edge to load against. A toe lock is more aggressive retention hardware that can catch your foot when you need to step away.
Why it matters for off-road
On flat pavement, your weight holds you on the pedals. In normal off-road, spiked pedals, shaped pedal edges, and power pads solve the retention problem for almost everyone. Toe locks start to make sense only when the wheel is leaving the ground on purpose and built-in toe or heel risers are not enough. The foot straps and toe locks article gives the full reality check.
The risk
If you crash with toe locks, your foot might not release cleanly. The same hardware that helps keep the shoe connected during a hop can keep it connected during a mistake. That is the trade-off.
555 take
Toe locks are not the normal off-road upgrade path. For almost everyone, spiked pedals plus power pads are the setup that matters. Separate locks belong to riders deliberately pushing jump and freestyle use cases.