Cubital tunnel entrapment (the tendinous arch that joins the heads of flexor carpi ulnaris).
Guyon’s canal (aka Guyon’s tunnel) formed from the palmar carpal ligament.
The vast majority of Guyon canal entrapments only affect the deep, motor branch, which passes between the hook of the hamate and the pisiform bone.
Fracture of the hook of the hamate can cause ulnar neuropathy.
Weakness pattern
Ulnar neuropathy produces weakness of the medial flexors and a more restricted clawing of the hand, so-called ulnar claw, with clawing of digits 4 and 5 (vs Klumpke's palsy affects both median and ulnar nerve distal musculature).
Note that 4th and 5th digit clawing forms the shape of a Pope's blessing and thus is also called the Benediction Sign.