As we go through our day-to-day life, we find it very difficult to find a time and place to stop and be mindful, even if only for a few moments.
Mindfulness is being in the present moment. So anything that brings us back to the present moment long enough to become aware that we could/should/can be mindful for even a moment or two is helpful to our daily practice.
An example of this could be, for instance, a stone you keep in your pocket or a strategically placed plant.
We call these things an anchor because it anchors us in the present moment.
When you feel or see the anchor it serves as a present moment reminder.