In general there are four styles of "boots". They may be high or low, hard or soft.
Soft boots are made of softened leather all the way around, much like moccassins. They are pliable, light-weight, and will protect the foot against most normal hazards, including sharp stones, hot or cold floors, liquids such as spilled acid. They do not protect against certain artificial hazards. It is not possible to kick open a door in soft boots, and any attempt to do so will cause injury to the foot; nor is it possible to pass through caltrops without great care.
Hard boots are made of stiff leather which is reinforced by a second layer overall and additional strips and caps at key points; it is stitched to a hard sole, often of thick cured hide but usually of wood. A person in such boots can pass through an area of caltrops unharmed, and may not even be slowed. These will protect the feet against most hazards. However, it is not possible to move silently in such boots, whether by thief skill or by racial abilities or by any other means; the boots will bang on the floor in such a way that they are easily heard. Also, hard boots make climbing impossible, for walls, ropes, or any other surface except hills, ladders, ramps, and stairs. A character in hard boots must either be hoisted by others, or have sufficient upper body strength to lift himself and his equipment up a rope by arms only; this is only possible if the character is less than 50% encumbered. Because they tend to be stiff, no martial arts kick attacks may be done in hard boots.
High boots reach to the knees, limiting flexion of the ankle and impeding flexion of the knee slightly. No climbing can be done in high boots (except as for hard boots), and running, jumping, and certain skills such as pole vaulting and tightrope walking will be slightly penalized. However, the boots will partially protect against certain attacks which are low to the ground, such as the bite of giant centipedes. Further, there is room in high boots to hide certain items, such as daggers, wands, and other items which are of similar shape. The boots lace up above the middle of the calf, but are open at the top to permit better freedom of motion. Because they limit movement, no martial arts attacks which rely on the foot or leg may be performed in high boots.
Low boots end mid-ankle. They provide no protection to the lower leg at all, but they receive no penalties for any type of movement. However, these are laced tight around the top, and it is not feasible to hide anything inside a low boot.
Sandals may be worn by any character who wishes. These do not protect the feet against anything except the ground, such as sharp stone, cold or hot floors, or liquids. It is not possible to kick open a door in sandals except by such martial arts special maneuvers as Crushing Blow. Sandals neither benefit nor impede martial arts. They have a hard sole, and so do hinder moving silently as hard boots.
Certain characters may choose to go barefoot. Most oriental classes who are not generally accustomed to heavy armor are quite accustomed to the natural hazards of the woods and the roads against the bare soles of the feet, and will suffer no movement penalty. Monks, Shukenja, Kensai, Ninja, and Wu Jen certainly have this option. The foot is not protected even against sharp stone, hot and cold floors, or liquids (obviously), but there is no hinderance to movement, and it is possible to move silently in bare feet. Ninja and others will frequently wear Tabi (socks), which is functionally the same for game purposes, but will keep the foot warm in normal cold situations.