How to annex two rigid bodies

hello, i was wondering what is the simplest solution of annexing two rigid bodies - something like rigid joint. if force affects first body, then second also feel that. i need it to create one rigid body and be able to add forces for small parts of this body. i've tried hinge with angle limit and custom joints, but i think it isn't optimal solution.
edit: i have problem with prebuilt CustomRigidJoint - is is needed to set some custom callbacks?


sorry of my english,

thanks.