The mountain path is so narrow that only one person can pass at a time.
Tips
culture
Most learners meet 仄 in 平仄 (píngzè), the bedrock of classical Chinese prosody. 平 = level tone (modern 1st & 2nd tones); 仄 = oblique = old 上声 (rising), 去声 (falling), 入声 (entering) — modern 3rd, 4th, and historic 入声 syllables.
memory
The character itself is a picture of obliqueness: 人 (a person) tucked sideways under 厂 (a cliff) — leaning, narrow, uneasy. The shape encodes all three meanings.