left hand, old grass radical (no. 45)
屮 is a rare kanji with two disconnected meanings: it can represent a left hand, or it can serve as the old grass radical (no. 45). These senses do not share a clear conceptual center.
The exact historical origin of 屮 is uncertain. It may have originally depicted a left hand or a sprouting plant, but the modern form is too abstract to confirm a single source.
The shape looks like a hand with three fingers extended to the left, or like a small plant with three blades of grass. Remember it as either a left hand or the old grass radical.
For テツ, imagine a left hand made of iron (鉄, てつ) that never gets tired: 鉄 -> テツ, and the hand is strong like metal.