Don't confuse 凸出 (tūchū, physically protrude/bulge) with 突出 (tūchū, to stand out / be prominent / outstanding). They share the same pinyin but 凸 is concrete and physical, while 突 is figurative — 突出的成绩 "outstanding achievements," not 凸出的成绩.
memory
Look at the character 凸 — it literally is a shape with a bump sticking up out of it. The character is its own picture.
