Written by Dr. Jody Muelaner
A hasp and a latch are both types of fastening used to hold a door or gate closed. A hasp is a slotted plate that fits over a loop before a pin is inserted through the loop, securing the hasp. A padlock may also be inserted through the loop, instead of a pin. Essentially, a latch is a fastening that engages with a catch, keeper or strike plate to hold the door closed.
A hasp works as a type of door fastener and requires a pin or picklock. In this image, a Suffolk latch is on the left and a modern hasp on the right.
Hasps can be easily produced using primitive manufacturing methods and have been found on Roman sites dated to the first century, where they were used to secure removable lids to chests. These simple hasps, made of bronze, consisted of a bar with a hole at each end. The hole at one end was nailed to the chest while a larger hole at the other end passed through a loop attached to the lid.
Modern hasps have a hinged strap made from sheet steel with a slot to fits over a staple, which is designed to receive a padlock. Some hasps have a built-in lock replacing the staple, the hasp is placed over the lock which is then rotated and locked in place securing the hasp behind it.
Latches vary greatly in design and complexity, one type of early door latch, the Suffolk latch, was named by the 19th century British architect, William Twopenny. However, its design dates to the 16th century. Traditionally made from wood or hand-forged iron, the Suffolk latch features a bar that fits into a notch or slot, which is lifted by a lever or string from either side.
Modern door latches include the spring latch, or latchbolt — a bolt with an angled end that’s spring-loaded to allow it to retract when engaging with the strike plate and automatically extend into the strike plate once the door is closed. This feature allows the engagement of the latch through the closing of the door while the latch is disengaged by turning a handle.
The cam, or twist, latch, features a cam which rotates in the base to engage and squeeze the object being fastened, and are often used to secure cabinet doors. The pulldown, toggle, tension, or draw latch, features a loop or claw which catches onto a catch plate and is pulled against it by a lever arm, these latches are commonly used to secure toolboxes and cases. All latches include one part which grasps another to secure two components together.
One latch that may confuse users due to its similarity in appearance to a hasp, is the cabin hook, or eye latch, a hooked bar, which grasps onto an eye mounted on the adjacent surface being fastened. Cabin hooks, often used to secure doors in an open position, take their name from the need for ships to secure their doors from opening and closing as they pitch and roll.
Filed Under: Clamps • locks • latches