(i) Closed shackle design
In this case, the body has its shoulders raised to conceal as much length of the shackle as possible, leaving a small section that is hard to access for attacking. This is the design preferred in industries with high-security needs such as banking and courier.
However, the small clearance makes it difficult to lock lockers with concealed hasps and chain links.
(ii) Open design
The open design is a diametric opposite of the closed design. The full or almost all the shackle length is exposed, which makes it easy to loop the padlock through large bars, hasps, links, etc.
However, the longer exposure of the shackle makes it much easier to cut, pick or break and thus the padlock may not provide a high level of security.
(iii) Semi-enclosed design
This is a sandwich of the above two designs. The shackle length tries to balance between security from attack and the flexibility of use.
(iv) Long design
In this case, the shackle is extra-long and this provides for locking extra-large lockers and noosing multiple hasps, chain links, fittings, and so on.
However, when targeted by a burglar, he has more than enough space to cut or break it open.
(v) Adjustable shackle padlock
This lock provides an innovative way to adjust the shackle length to suit your purpose of use. The padlock, however, needs regular lubrication to prevent the shackle from getting jammed by rust, dirt, and grime.
For domestic uses such as the school or gym lockers, where there is a mid-level risk of attack, the semi-enclosed and adjustable shackle designs have proven to be the best. They provide you a reasonable clearance for a sweat-free locking in the concealed hasps but still making it difficult for a burglar to succeed in his ways.
Padlock shackle material
Just like design, the purpose of use will dictate the type of padlock material that you should choose, from both economic and security perspectives. Higher quality padlocks are more durable and harder to cut or pick. However, such materials are extremely expensive and however tough they are, it wouldn’t be economical to use them for some applications.
Molybdenum is arguably the strongest of all the padlock materials, most reliable, and weather resistant. However, it is also very expensive such that it only makes sense of use in industries such as defense and nuclear.
A low abundance element, boron is developed into a high-strength and lightweight material that finds use in several industrial applications. For use in padlock a number of boron variants are used including;
Boron alloy that provides high-level security. The shackle features supreme tensile strength and cut resistance.
Boron hardened steel which is high-grade steel, heat-treated to resist any saw or bolt cutting or any other tampering device. Its ultra-high strength is perfect for high-tech industries such as automotive.
Boron steel that is also strong and reliably safe, making these padlocks suitable for heavy-duty industrial use.
(iii) Heavy-duty steel
This is a type of hardened steel that is attack resistant and durable. Steel is hardened by heat treating, enabling it to withstand severe human tampering. It is, therefore, safe for use in both high-security and general purpose applications such as banking and homes. Most of these padlocks also have weather resistive chrome or zinc coating.
Brass is lightweight and brittle and thus it finds use in applications with a low risk of burglary, acting just to lock the locker. However, brass is weather resistant, making this lock perfect for outdoor use.
This is a lightweight, cheap and low-security material. However, the lock is not entirely worthless as it can be the safest where there is a risk of electrocution, as long as security is not a major issue.