First, make a list of design requirement (a.k.a. specifications, wants, constraints) that would be appropriate for this type of mechanism. Then, identify metrics that will allow you to assess each design requirement. Then, list target values or ranges of target values where appropriate. Develop one high level concept that is not in violation of any of your design requirements (it doesn’t have to meet all of them, but it can’t violate any). Describe this in words AND with some sort illustration. This can be a clean sketch by hand, or a screenshot of a Solidworks assembly.