step stool; small stepladder
A physical object used to reach high places, such as a stool or small stepladder.
I used a step stool to get something from the high shelf.
I stood on a small stepladder and changed the light bulb.
Figurative use: a means to an end, often for career advancement or achieving a goal.
I want to use this job as a stepping stone to become independent in the future.
He used that position as a springboard for his career advancement.
踏み台 literally means a stepping stool and is often used to mean using someone or something merely as a means to one's own advancement, whereas 足掛かり is more neutral, simply describing a starting point for progress.
Standard kanji spelling; the most common written form.
Variant spelling without okurigana; less common but still used.
Compound of 踏み (fumi, 'stepping', from verb 踏む) + 台 (dai, 'stand, platform').