In bi-siqṭ al-liwā, the bāʾ is a preposition, siqṭ is the first term of a construct phrase, and al-liwā completes it. The commentary associates siqṭ with the edge or interruption of a sand formation, and liwā with curved sand.
Bayna al-Dakhūl fa-Ḥawmal identifies two place names. The poet does not describe an abstract “distant home”; he locates an abandoned campsite between recognizable landmarks.
These names are not a dry geographical list. They give a remembered experience a definite landscape.