If you search for “crossing the midline” on Google you will get a lot of information. I will try to summarize it briefly.

What is the diameter?
The midline is an imaginary line in the middle of the body. Crossing is the ability to reach across the middle of the body with the arms and legs.

This allows children to cross over their body to perform a task on the other side of their body. So it is an opportunity to move a hand or foot into the space of the other side. We cross the midline when we scratch an elbow, cross our ankles, and read from left to right.

Why cross the midline?
Crossing the midline helps build connections in the brain.

It is an important prerequisite skill needed for the proper development of various motor and cognitive skills.

What does this have to do with dominant hand?
Both sides of the brain need to talk to each other for the “dominant hand” and the “supporting hand” to work together and complement each other.

Coordinating both sides of the body may be difficult for the child who does not cross the midline.
Developing a preferred hand is a sign that the brain is maturing and developing the ability to cross the midline.

And what does this have to do with reading?
Having difficulty crossing the midline also makes it difficult to track a moving object from side to side or to read from left to right, which can also delay learning to read.

Why don't I notice anything?
Crossing the midline is something we all do every day. You may not realize it because it is an integrated movement in our bodies from childhood.

“Our son has been crawling for a few months now, so he has already achieved a crucial achievement in reading and writing.”
Wait, what? Yes, because crawling is one of the first ways babies move their right and left sides of their bodies separately! In natural development, the crossing of the midline is already being prepared.
What does it look like when your child has difficulty crossing the midline?

Your child may be stuck in the middle of their body and need to switch hands to continue. Or they may compensate by shifting their entire body to the opposite side.

And now finally the most fun part: Practicing while playing!

My sources and certainly interesting websites on this topic

teachmama.com
growinghandsonkids.com
childrenparenting.com
childdevelopment.com.au

Images:
slimmerschrijven.nl