Maria E. Beasley, (Philadelphia, 1847-1904) was an American entrepreneur and inventor, who designed two improved lifeboat models, used among others on the Titanic.  
Look at Maria Beasley's plans for her ‘fireproof, compact, safe and easy to launch’ life raft. Her design included handrails surrounding the raft and rectangular metal floats. This design is capable of folding and unfolding, making it easy to store, even with the rails.

a) What type of structures can you observe in them?

b) Are they fixed or articulated structures?

c) Prior to Beasley's design, life rafts were typically flat wooden planks.  What type of structure was it? 

d) The concepts of handrails and reduced storage size are still used today, although their exact designs have changed. What type of structure is used today for life rafts?