The front of the anti-skid pedal pad in the bathroom is lawn-like, which increases the roughness of the contact surface under certain pressure, thus increasing the friction between the foot and the pad.

There are many small suction cups on the back of the anti-skid pad. After the air in the suction cups is squeezed out, the suction cups are squeezed to the ground under the action of atmospheric pressure, which plays an anti-skid role.

So the answer is: increase the roughness of the contact surface.