on the wall和in the wall的区别主要在于含义及用法上。on the wall中文翻译为“在墙上”、“墙表面的事物”，强调在墙的表面；in the wall中文翻译为“在墙里面”，侧重强调在墙的里面。

on the wall意为在墙上;例如在墙的平面上挂幅画;墙表面的事物。

例句：The cat was on the wall, watching for birds.

那只猫在墙上伺机捕捉鸟儿。

The sign on the wall said 'Now wash your hands'.

墙上的牌子上写着“请洗手”。

I scraped the side of my car on the wall.

我车的一侧被墙刮了。

His eyes wandered towards the photographs on the wall.

他的目光慢慢地移向墙上的照片。

The child kept her eyes fixed on the wall behind him.

这个小女孩眼睛一直紧盯着他身后的那堵墙。

I jumped on the wall to grab the attention of the crowd.

为了吸引那群人的注意，我纵身跃上墙头。

She sipped her coffee and straightened a picture on the wall.

她抿了口咖啡，然后把墙上的一幅画扶正。

He flicked a light-switch on the wall beside the door

他啪的一声打开了门边墙上的电灯开关。

Above him, in a niche on the wall, sat a tiny veiled Ganesh, the elephant god

在他上方墙上的壁龛里安放着一尊极小的蒙面象头神伽内什的塑像。

in the wall意为在墙上;在墙里面。

例句：They managed to knock a hole in the wall.

他们设法在墙上凿了个洞。

A number of thin cracks appeared in the wall.

墙上出现了许多细裂缝。

Cracks appeared in the wall and a door jammed shut

墙上出现了裂缝，一扇门卡住打不开了。

Wind came through a chink in the wall.

风从墙上的裂缝中透了进来。

Through a chink in the wall she could see a bit of the blue sky.

透过墙上的缝隙她可以看到一线蓝天。

Beams of light came through the cracks in the wall.

束束光线透过墙上的裂缝照进屋里。