Abstract: A locking structure for a spring-loaded, pushbutton pin coupler, the inveon prevents inadvertent or accidental depression of a "button latch" pin which can result in an uncoupled joint. The present locking structure cooperates with a pushbutton pin connector such as is commonly used on collapsible or extendible arms or legs. According to the invention, a conventional button latch pin is provided with a locking plate at its inner end, rotation of the pin after coupling of joint with the pin causes the locking plate to also rotate into engagement with a fixed pin element carried by the structure coupled by the pin, thereby preventing displacement of the pin from the locked position.

Abstract: A collapsible restraint is provided for attachment to the end of a flexible easuring tape in order to allow the thickness of a material, such as an ice layer covering a lake or other body of water, to be measured through a hole in the material. The collapsible restraint includes first and second pivotally connected blades which are maintained in a fully extended position by a locking arrangement to allow the blades to engage the bottom opening of the hole. The locking arrangement can be disabled by an upward pull on the flexible measuring tape in order to cause the blades to pivot to a collapsed position, thereby permitting the restraint to be withdrawn from the hole.