#include <bits/stdc++.h>
using namespace std;
long long q, n, xk, yk, a, b, t, k;
pair<long long, long long> pos[1003];
string s;
int main() {
  cin >> q;
  for (int i = 1; i <= q; i++) {
    cin >> n;
    for (int j = 1; j <= n; j++) {
      cin >> xk >> yk;
      pos[j].second = xk;
      pos[j].first = yk;
    }
    k = 0;
    pos[0].second = 0;
    pos[0].first = 0;
    sort(pos + 1, pos + n + 1);
    for (int j = 1; j <= n; j++) {
      if (pos[j].second < pos[j - 1].second) {
        k = -1;
        break;
      }
    }
    if (k == -1)
      cout << "NO" << endl;
    else {
      cout << "YES" << endl;
      for (int j = 1; j <= n; j++) {
        if (pos[j - 1].second == pos[j].second)
          for (int z = pos[j - 1].first; z < pos[j].first; z++) cout << 'U';
        else {
          for (int z = pos[j - 1].second; z < pos[j].second; z++) cout << 'R';
          for (int z = pos[j - 1].first; z < pos[j].first; z++) cout << 'U';
        }
      }
      cout << endl;
    }
  }
}
