Recovery hardware refers to all the parts of the recovery system that connect shock cord to other shock cord, parachutes, or the rocket. It is usually purchased off-the-shelf, and manufacturing it yourself is not recommended. It has to stand up to very extreme forces to function properly. 

Disallowed Materials & Designs

While is is very common for hardware used in recovery to be commercially available made of stainless steel, it cannot be used for recovery systems in many applications. Its use in NAR launches is dubious, and IREC has outright banned any load bearing components made of stainless steel in Section 6.2.1 of the IREC Design Test and Evaluation Guidelines. It is not ideal for the shock forces of recovery and will not fail as gradually as other materials.

Under the IREC Design Test and Evaluation Guidelines, Section 6.2.2, "bent wire" recovery hardware is banned. These can be identified by the fact that the end of the loop does not perfectly join up to the start of the loop, it is constructed from a piece of bent rod. IREC only allows the use of forged recovery hardware, where the loop is one sealed shape that is cast or machined all at once. While "bent wire" hardware can be used for NAR or TRA launches, it is still best to minimize the use of these forms of recovery hardware.

Recovery Hardware Rating

Recovery hardware is rated by the load it can sustain in pounds. For something that is designed for use with rocketry recovery systems, like a purpose-bought swivel link from Apogee Rockets, a factor of safety of 1.25 to 1.5 can be used. For recovery hardware not intended for use with rocketry recovery systems, like a general-purpose eyebolt from McMaster-Carr, a factor of safety of 2 to 2.5 should be used.

Eyebolt and Eyenut

Eyebolts and eyenuts are used to connect shock cord to the rocket through a bolt hole. Eyebolts, as the name implies, have a tie-down eye on the top of a threaded rod, whereas an eyenut has a threaded hole at the base of a tie-down eye to accept a threaded rod or bolt. U-bolts serve a similar purpose to eyebolts and eyenuts, but are distinctly different in that they have two threaded connectors, that allow them to be mounted in a way that it does not interfere with the area directly below the cord tie-off point. 

When installing recovery hardware, make sure to put a washer on both sides of the recovery plate, if the part does not already have a flange built in (i.e. eyenuts usually have one as part of the design). 

When securing an eyebolt or eyenut, it is important to cross-pin or cross-lock it. The force of recovery systems can use the eyebolt or eyenut to spin, which can unthread it from the best of the rocket. To prevent this, a Nylock nut, a jam nut, or a cross-drilled thread wire should be used. If the eyebolt or eyenut never has to come out again, coating the threads and nut/bolt in epoxy can work as well.

Quick Link

Quick links, sometimes referred to as "threaded carabiners" are used to connect together two length objects, usually shock cord to shock cord or shock cord to parachute.. Quick links can also be used to connect to eyebolts or similar, but you have to be careful. The rubbing of metal-on-metal will lead to wear and wallowing over time. 

Quick links are different from carabiners in that they are threaded to close, instead of being spring-loaded. This means that they can sustain a greater load and are less likely to open during use. 

Swivel Link

A swivel link is placed inline with the shock cord between a parachute and the rest of the rocket to reduce spinning. Parachutes can spin a lot when deployed, which can cause twisting in the shock cord (reducing its effective load), or causing issues with cameras and avionics onboard. Swivel links are usually just two eyes constrained with a spherical joint. While they are not necessary for most rockets, they do help make things a lot smoother. They are usually hard to find for very high loads.