Source: Batad Ifugao dictionary
The hinālung is a double-edged dagger or sometimes as large as a shortsword. They typically have a tang that is rolled into a socket of oval cross-section.1
A large shortsword type hinālung with scabbard.
Mandarin Mansion inventory 2022.
In the literature
A Batad Ifugao dictionary says the following:
"A double-bladed bolo of various lengths, usually carried for self defense; large varieties are sometimes used for cutting trees."
"A double-bladed bolo is in one metal piece with a rolled handle, hālung, usually covered with a woven rattan handle covering, allūbung. One variety has a rolled handle base into which a wooden shaft may be inserted to be used, especially in the forest, as a spear." 2
I am personally skeptical about their use as a spearhead, for the following reasons:
1. I am not aware of such use ever being documented. Guesswork by non-native observers?
2. Ifugao spears are typically tanged, not socketed.
3. Most men carried a spear or javelin anyway. Why would one need a knife that could be made into one? Especially since it's about as much effort to carry a spare headless shaft as it would be just to carry a complete spear.
1. Some more examples can be seen at vikingsword.com.
2. Sil Philippines Languages entry hinālung.